October 1999, Number 28

As many of you may have noticed, a July 1999 issue of the NAIC Arecibo Observatory Newsletter was not published. This was due to unforseen and unavoidable technical difficulties. The result is this “double” newsletter, something we (and, no doubt, you) would be happy to avoid in the future. We regret any inconvenience caused to our readers. – The Editors

Understanding Pulsar Weather Joanna Rankin, Physics Dept., Univer- sity of Vermont, Burlington, VT While radio pulsars have proved so very important to astrophysics over the last three decades, results to date of the great efforts made to understand the physical mechanisms of their radio emissions can only be regarded as frustrating and dis-

INDEX Understanding Pulsar Weather 1 Radio Astronomy Highlights ..... 4 Zeeman Splitting a New Result. 9 SETI Observations at Arecibo 11 Space & Atmospheric Sciences 12 New Space and Atmospheric Sciences Program ...... 13 Planetary Radar ...... 18 Secondary Adjustment...... 20 New Era in Communications .. 20 Pulsar Astronomy Seminars .... 20 LAN Upgrade ...... 21 AOVEF News ...... 23 Summer Student Program ...... 25 Fig. 1: A short sequence of “drifting sub-pulses” from pulsar B0943+10. Pulse number (or revolution) is on Service Observing Specialist ... 28 the vertical axis, which is plotted against rotational phase or “longitude”. The average profile is given in Employee of the Year ...... 28 the bottom panel, and the pulse energy in the left-hand panel. Comings and Goings ...... 29

The NAIC is operated by Cornell University under a Cooperative Agreement with the National Science Foundation. appointing. Some progress has been Average profile Fluctuation Spectra made, but in baby steps rather than great 50 (longitude-resolved) leaps of insight. While physical models of pulsar radio emissions are the subject of hundreds of articles and several books, no such theory has been successfully ap- plied in a detailed manner to the obser- vations of even a single pulsar. This is bad! One wonders whether young grad- uate students should be discouraged from having anything to do with this benight- 010 ed area! longitude (deg.) Somewhat by chance, however, study of one pulsar seems to be reopening these unpromising questions, providing imag- -10 es and insights, prompting development of new techniques, and very possibly of- fering routes of approach to understand- 150 ing many of the “classical” phenomena that pulsars exhibit in their radio pulse 100 sequences. 50 The pulsar is an obscure object known as B0943+10, which is so weak 0 0.1 0.2 0.3 0.4 that its pulse sequences have only so far frequency*P been observed with the Arecibo instru- ment − though it was discovered (quite early in 1970) at 102 MHz using the Fig. 2: Fluctuation-power spectra (center panel) as a function of pulse longitude and frequency as well as the integral spectrum (bottom panel) of B0943+10. Note the primary and secondary features at about 0.46 and Pushchino Observatory of the Lebedev 0.07 cycles/period as well as the symmetrical “sidebands” around the former. Physical Institute in the then Soviet Union. Even at Arecibo, it is a poor pros- mode, whereas the last 170 have it just so happened that Deshpande had pect, and had it not been for the wonder- switched to the weaker, disorganized already developed some new strategies ful accident that Pushchino colleagues “Q” mode. This very sequence provid- for studying pulsar fluctuations that suf- Svetlana Suleymanova and Vera Izvek- ed the first opportunity to study the pul- fer from aliasing. ova were able to join a 1992 pulsar po- sar’s “profile modes” at 430 MHz, and A typical “B” mode pulse sequence larimetry project organized by myself it was the first-ever observation to actu- is shown in Fig. 1, where the intensity is and then postdoc N. Rathnasree, we ally “catch” a “B” – to – “Q” mode tran- plotted against both pulse number and would probably have never put this star sition. Just at this level, the results were longitude, with the former average (pro- on the source list. Svetlana, however, very interesting, and a report was pub- file) at the bottom and the latter at the has a “special relationship” with this lished last year (Suleymanova et al. 1998 left. The characteristic diagonal “drift” “Russian” pulsar, and she simply would JAA 19, 1). not take “no” for an answer! This was bands and near-alternate-pulse modula- also a time of overpowering 430-MHz During the course of this work, how- tion are quite evident. Note also the ex- interference at Arecibo, but through ever, pursued during several visits to the ceptionally strong individual pulses at an some miracle the US Navy and other Raman Research Institute in Bangalore, interval of about 40 periods. Comput- spectral villains kept their peace for the Avinash Deshpande and I discovered ing the fluctuation-power spectra for duration of this observation. that B0943+10 has by far the most ac- each longitude, we obtain the result in curate and stable pattern of drifting sub- Fig. 2. Note the primary feature at ~0.46 The resulting 18-minute, 986-pulse pulses of any known pulsar − cycles/period (c/P), which reflects the ap- sequence is certainly the highest quality considerably more so than the pulsar proximately even-odd modulation pat- observation ever recorded on this star usually mentioned in this connection, tern; it is unresolved in this 256-point and was well calibrated both in polar- B0809+74. The 1992 October sequence Fourier transform as well as in longer ization and intensity. Its first 816 pulses was so stable that we might even be ones – therefore its Q must be at least are in its bright, regularly drifting “B” tempted to call it “coherent”. Moreover, 500!

October 1999, Number 28 2 NAIC/AO Newsletter Fig. 2 shows four clear modulation ed by the 0.027-c/P “sideband” spacing emission pattern poleward of the mag- features, two more than have ever been unambiguously indicates that there are netic axis with a –4.3° impact angle. seen before in the fluctuation spectra of just 20 such sub-beams. The circulation This geometrical information, together any pulsar. Our problem is to understand time of a given sub-beam is then just 20 with the sense of the polarization-angle their relationship and the emission con- times the 1.87-P interval between adja- traverse, remarkably permits us to de- figuration which they represent. First, cent sub-beams or some 37.3 periods. To termine the absolute directions of rota- we must understand whether these fea- test this hypothesis, we can fold the en- tion of both the pulsar and the sub-beam tures reflect the actual modulation fre- tire sequence at this interval, and, indeed, pattern. Simple-minded arguments suf- quency, or whether they are aliases of it shows just 20 clear emission elements, fice to show that the sub-beams rotate − faster fluctuations that cannot be ade- with some 2-3 times as bright as others! that is, their tracks are circular. quately sampled at the slow rate at which A good deal is known about the emis- With these factors at hand, we have the star’s rotation brings the “window” sion geometry of B0943+10, because it been able to map the sub-beam pattern of emission back into our view. Or, said can be observed over a wide range of of pulsar B0943+10 using what we call differently, it cannot easily be decided frequency and the observed widths of its a “cartographic” transform. The ob- whether the “drift” in Fig. 1 is to the right profiles modeled. We find that the star’s served sequence, in terms of pulse num- or to the left and whether the sub-pulses rotation and magnetic axes are closely ber and pulse longitude, is simply move just a little from pulse to pulse or aligned at an angle of 11.6°, and that our mapped back into the frame rotating a lot. sightline makes an angle of 7.3° to its around the magnetic axis of the star – To make a long story short, we have spin axis; therefore, the sightline cuts the that is, using a magnetic polar coordi- been able to resolve the aliasing by tak- ing the approach of computing a fluctu- ation spectrum of the entire sequence with the unsampled regions between suc- cessive pulses interpolated with zeros. This involves a Fourier transforms of up to a million points, uses the circumstance that the fluctuations are continuously sampled within each pulse, and permits us to explore the harmonic structure of each feature. On this basis we find that the primary feature is in fact the first- order alias of an actual 0.535 c/P phase modulation, and that the secondary fea- ture (at ~0.07 c/P) is the second-order alias of its second harmonic at about 1.07 c/P. This explains the even-odd sub- pulse pattern, because 1/0.535 c/P = 1.87 P/c is the interval between sub-pulses at a given longitude. It also indicates that the sub-pulses “drift” from right to left (negatively) – that is, in the same direc- tion as the star’s rotation. We can also understand the pair of symmetrical features on either side of the principal one as indicative of an ampli- tude modulation on the phase modula- tion. If the “drifting” sub-pulses are produced by a system of sub-beams, ro- tating around the star’s magnetic axis, then just such a pair of “sidebands” Fig. 3: Map of the sub-beam pattern projected onto pulsar B0943+10’s magnetic polar cap. The sub-beams would result if some of the sub-beams rotate counter-clockwise, making a complete circuit every 41 seconds; whereas the pulsar rotates on its axis are significantly stronger than others. (shown as up in the map) every 1.1 seconds in a clockwise direction. The path of our sight line to the star is The 0.535-c/P feature frequency divid- also indicated in the upper part of the map.

October 1999, Number 28 3 NAIC/AO Newsletter nate system rotating at the sub-beam cir- More recently, we have confirmed Pulsar B0943+10 then appears to culation rate. Such a map is shown in the 20-sub-beam structure in two older have taught us a number of lessons: that Fig. 3, with the star’s rotational pole Arecibo sequences, one at 430 MHz “gap” discharges are not spacially con- “up”, the magnetic pole in the center of from 1972 and another at 111.5 MHz tinuous, but occur in columns, which can the diagram, and a portion of the sight- from 1992, and graduate student Ashish be stable over many circulations; that line traverse indicated. Note the 20-fold Asgekar has also done so using a 34- whatever the “action” that drives pulsar sub-beam pattern. (Additional still and MHz sequence recorded in 1998 at the emission it moves and cannot therefore moving images of pulsar B0943+10’s Gauribidnur Array in India. Maps have be a property either of the stellar surface “weather” can be seen on the web at also been constructed in full polariza- or the fields; and that some pulsars are http://www.rri.res.in/~desh or http:// tion, which show the sub-beam structure rather efficient in converting their stored www.uvm.edu/~jmrankin under “What’s in terms of the linear and circular power rotational energy into radio emission. New?”.) in the pulsar’s two polarization modes. Consequently, we believe that these The elliptically orthogonal nature of the Many aspects of this diagram are re- techniques hold considerable promise for modal polarization, long seen in various markable: The sub-beam pattern appears shedding new light on the pulsar emis- observations, is especially striking as to represent a system of plasma columns sion problem. We have been able to ob- displayed in the sub-beam maps. Fur- which start at the star’s polar cap, stream tain preliminary maps of several other thermore, it has also proved possible to out through the radio emission region, pulsars with geometrical configurations map the pulsar’s emission pattern and “up” toward the light-cylinder. At something like that of B0943+10 and through the transition from its regular the stellar surface, the ring of plasma col- plan to slowly work inward to consider “B” mode to its chaotic “Q” mode – umns is no more than some 145 meters pulsars where the sightline passes more implying that the circulation time re- in radius – making their spacing less than centrally across the magnetic axis of the mains nearly the same despite the dra- 45 meters and size hardly 20 meters. star. In the course of this project, we matic change in observed emission-all Each of these plasma columns, howev- encounter many of the “classical” prob- the while providing insight into the na- er, carries some 2×1023 Watts, or about lems of pulsar radiation: core and conal ture of these “profile” mode changes. 10-3 of a Solar luminosity! beams, nested cones, modes, nulls, etc. However insightful this one pulsar Some of our results were presented in These observations also permit us to B0943+10 has proved to be, should we September at the IAU Colloquium #177 explore phenomena in the polar-cap regard it as utterly unique? Yes & no! in Bonn, Germany. “gap” region, where physical conditions We know of no other pulsar which comes are some of the most “exotic” anywhere close to matching its “B” mode preci- in the cosmos – with magnetic fields of sion and stability. In this sense it is thus the order of 1012 Gauss and an electric far unique, because this stability reflects Radio Astronomy Highlights potential across this “gap” of some 1012 the orderly sub-beam fluctuations which Duncan Lorimer and Chris Salter Volts! One theory, published 25 years permit its overall configuration to be de- ago by Malvin Ruderman & Peter Suth- coded without invoking other assump- erland at Columbia University (1975 Ap. HI in External Galaxies tions. However, other pulsars appear to J. 196, 51) anticipated that electrical dis- have predictable circulation times with- In a very productive visit to Arecibo, charges – what they called “sparks” – out having as regular a “drift” pattern. Chris Impey & Valorie Burkholder would form in the polar-cap “gap” and We simply do not yet know what are the (Steward Observatory) measured the that these “sparks” would circulated un- λ conditions which produce a B0943+10. 21-cm HI emission of low surface der the action of E×B drift. Using this “Null” pulses are well known to disrupt brightness (LSB) galaxies taken from an simple formalism, we are able to square an otherwise regular “drift” pattern (as optical sample selected on UKSTU our observed 41-sec circulation time in pulsar B0809+74), and it is probably plates. During the course of a ten-day with anticipated polar-cap conditions, as significant that no “null” pulse has ever run, they observed more than 100 galax- long as the radius of the plasma-column been identified in B0943+10. Were the ies with a detection rate of over 50%. “feet” is about 75 m and the “gap” po- 9 sub-beams unevenly spaced in magnet- The average HI mass detected was 10 tential is somewhat lower than expected M , though they did make several 108 ic azimuth or were their intensities not O (about 3×1011 V). These results are re- M detections for nearby galaxies. These stable for several circulation times, the O ported in more detail in two papers “drift” would appear quite irregular and observers were able to reduce the data (Deshpande & Rankin 1999, Ap. J., in any signature of a definite circulation on site and left Arecibo with a list of over press; and Deshpande & Rankin 1999, time would be much more difficult to 50 new detections and measures of HI MNRAS, to be submitted). discern. mass. They have learned that low sur- face brightness is most likely the result of low surface mass density, which in-

October 1999, Number 28 4 NAIC/AO Newsletter hibits star formation. Therefore, galax- quasar, Q1214+1804. The goal was to ies with higher surface brightness should look for gas-rich galaxies at small im- 2 have lower gas mass fractions (indicat- pact parameters to this line of sight, and ing more efficient star formation) and to subsequently relate the galaxies to 20 lower HI mass to blue luminosity. Fig. Ly-α absorbers in the quasar spectrum. 1 ¥ 4 shows the new detections, combined The redshift range 0 < Z < 0.2 was cov- ¥O O with results on the same sample from an ered in two correlator settings. In addi- ) (M /L ) ) (M /L B

/L earlier Arecibo run; this is among the tion to looking for galaxy counterparts HI 0 largest HI surveys of LSB galaxies ever to the diffuse hydrogen absorbers, the

Log (M carried out. There is a strong trend to- experiment provides an independent test wards higher gas content for a lower sur- of the blind HI surveys that define the

-1 face mass density of stars. HI mass function, work also done at Unfortunately, the simple interpretation Arecibo. Working over this broad red- 20 22 24 26 of this trend – LSB galaxies are young shift range exposed them to the full prob- O B and therefore unevolved – ignores the red lems of interference and other artifacts. optical colors and high metallicities of Fig. 5 shows the 1σ HI mass detection Fig. 4: The ratio of HI mass to blue luminosity plot- many of these galaxies. This enigmatic limit as a function of Z for about 2 hours ted against central brightness in the B-band for HI integration for tow of the configurations: detections from a LSB galaxy sample. (Courtesy Chris population is still not understood. Impey) low Z (top) and high Z (bottom). This In May 1999, Chris Impey & Cathy represents about half of the low-Z data Petry (Steward Observatory) obtained and a fifth of the high-Z data obtained. deep λ21-cm HI observations toward the

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Fig. 5: The 1-σ HI mass detection limit as a function of Z for about 2 hours On-Off data at low Z (top) and high Z (bottom). (Courtesy Chris Impey) RFI Notes From T.Ghosh: The degradation of detection limit at several z-ranges in this unprotected band is due to a number of military radars including a recently installed frequency-hopping system (‘–’ marked). There are also resonance modes at several frequencies in this range in the ‘L-wide’ receiver. For more information, see http://www.naic.edu/~tghosh/smarg/smarg-vig1.html.

October 1999, Number 28 5 NAIC/AO Newsletter The increasingly challenging astronom- ties of the Local Group. The survey was was mapped out over the course of the × 6 ical environment at lower frequencies is sensitive to HI masses of 5 10 MO at week-long observing run. clearly seen. The final pencil beam will the 5-σ level. After a first round of ob- reach a 5σ limit at Z = 0.08 of about servations in April, all 4.5-σ peaks in the × 8 Molecular-Line Studies 3 10 MO, and will cover sufficient vol- spectra were selected and re-observed in ume to detect 5-6 galaxies by their HI June with double the integration time. Jeremy Darling & Riccardo Giovanelli emission, in addition to any quasar ab- None of the peaks could be confirmed (Cornell) report the discovery of 11 OH sorbers that correspond to gas-rich gal- as being real HI detections. This null megamasers (OHMs) and one OH ab- axies. result places interesting upper limits on sorber, along with upper limits on the OH the space density of primordial gas luminosity of 54 other luminous infra- Galactic High Velocity Clouds clouds in galaxy groups. red galaxies at Z > 0.1. The new mega- (HVCs) have recently gained attention masers show a wide range of spectral as being massive gas clouds distributed Phil Choi & Anthony Gonzalez (UC properties, but are consistent with the throughout the Local Group. The HVCs Santa Cruz) have observed 12 galaxy extant set of 55 objects, 8 of which have could be primordial objects raining on clusters in the redshift range of 0.12 < Z Z > 0.1. The new OH detections are the the Galaxy, either as remnants from the < 0.26 (1130-1270 MHz) using a drift- preliminary results of an in-progress formation of the Local Group or as rep- scan observing mode. Mean integration Arecibo survey for OHMs which is ex- resentatives from an intergalactic popu- times of 4 hr per cluster were achieved pected to produce several dozen detec- lation of dark matter-dominated mini with the purpose of obtaining total clus- tions. The ultimate goal of the survey is halos in which hydrogen has collected ter HI masses. All of the clusters in the to calibrate the luminosity function of and remained stable on cosmological sample are already well observed at both OHMs to the low-Z galaxy merger rate time scales (Blitz et al. 1999, Ap. J., 514, X-ray and optical wavelengths, so by (0.1 < Z < 0.2), and to use this measure 818, and Braun & Burton 1999, A&A, combining that data with HI masses to estimate the merger rate at higher Z 341, 437). These mini halos are general- these observers will investigate the role using pointed and blind surveys. The ly predicted by semi-analytical simula- that the hot intracluster medium (X-ray) survey will also provide an enhanced tions of galaxy and group formation in and the cold galactic HI reservoir (ra- sample of OHMs for the study of their much larger numbers than can be ac- dio) have on the star-formation history environments, engines, lifetimes, and counted for by the known dwarf galaxy (optical) of the cluster. Despite work- structure. The selection criteria for can- population. Assuming that the HVCs are ing in a relatively unexplored region of didate OHMs require IRAS detection at dark matter dominated, with the fraction the radio spectrum, clean observations 60 µm, and Z > 0.1. The redshift limit is of hydrogen to total mass approximate- with stable baselines were successfully imposed by the RFI environment, while ly equal to 0.1, it can be shown that they obtained. In addition, a useful byprod- IRAS detection guarantees that candi- are gravitationally stable at typical dis- uct of these observations is that RFI in dates are luminous infrared galaxies, tances of 1 Mpc from the Local Group’s the frequency range of 1120-1280 MHz which are galaxy mergers (Clements et barycenter. Placed at those distances, the al. 1999, MNRAS, 302, 391). OHMs × 7 HVC HI masses are ~ 5 10 MO and typ- ical diameters are 30 kpc. If this extraga- lactic interpretation of HVCs is true, similar clouds are expected in other gal- axy groups. Martin Zwaan & Frank Briggs (Groningen) performed a target- ed survey for these clouds in 5 nearby galaxy groups at distances between 25 and 40 Mpc, for which the Arecibo beam matches the typical cloud size, and most clouds should be detectable within a few minutes. A total of 300 pointings were observed on square grids centered on the group’s barycenters. The pointings ex- tended to radii of 2 Mpc and thus cover different environments within each group. The selected groups cover a range Fig. 6: OH megamaser detection for IRAS 21272+2514. This OH megamaser is the third most luminous of compactness, group richness and to- known, (log LOH = 3.6). The arrows indicate the expected locations of the 1667- and 1665-MHz lines (left and tal HI mass centered around the proper- right, respectively) based on the optical heliocentric velocity from the PSCz redshift survey (Saunders 1999, private communication). (Courtesy Jeremy Darling)

October 1999, Number 28 6 NAIC/AO Newsletter require a high density of molecular gas, (a) (b) 19566+3423 19566+3423-- 24 April1999 an energetic population-inversion mech- 3200 3200 16aug 88 anism (such as shocks, AGN or star- 1612 MHz 1612 MHz 2400 2400 bursts), and a radio-continuum source to stimulate emission. Mergers are quite 1600 1600 efficient at shocking the ISM, funneling 800 800 0 0 gas into the centers of the merging gal- 200 axies, fueling AGN, and producing ) 2 jul89 1665 MHz 3000 1665 MHz 100

(mJy 2000 bursts of star formation, so we expect mergers to be ideal environments for the 0 Flux 1000 production of OHMs. The detection rate 0 is 1 in 6 to date, and a typical OHM de- -100 400 tection is shown in Fig. 6. 600 2 jul89 1667 MHz 1667 MHz 400 200 Murray Lewis (NAIC) has undertak- 200 en reobservation of OH/IR stars within the Arecibo sky in a program that has 0 0 -80 -40 0 -80 -40 0 been both a learning experience in spec- LRS Velocity (km / sec) LRS Velocity (km / sec) tral-line use of the 305-m telescope, and a happy blend of science with student Fig. 7: OH spectra of 19566+3423 at 1612, 1665 and 1667 MHz, a) in the late 1980’s, and b) on 24 April education. Its purpose is to obtain si- 1999. (Courtesy Murray Lewis) multaneous 1612, 1665, and 1667 MHz quality spectra for about 400 OH/IR stars brief, often < 1000 yr, while the dura- spectra are distantly reminiscent of identified in earlier surveys of color-se- tion of masers is even briefer. Thus, over IRC+10420, which has, however, always lected IRAS sources. Those observed 10 yr a few stars may exhibit intensity exhibited the same velocity range by summer students in 1998 & 1999 pro- changes well beyond the factor of ~3 as- throughout the 24 yr since its discovery. vided instant visual gratification, as they sociated with the regular pulsation cy- are obvious, have a recognized classic The IRAS satellite provided positions cle. The program has already scored norm, yet have diversity of morpholo- for many thick dust shells. At Arecibo, several successes in this regard. Thus, gy, intensity, and velocity range. These about 400 of these were confirmed as Ben Oppenheimer (REU student in data are also well suited to learning re- OH/IR stars by detecting their 1612- 1998) found the peak intensity in duction processes, with good feedback MHz masers, though up to 75% of can- 18455+0448 had dropped from 2000 to on both the software utilized and the didates remained undetected. These OH/ 200 mJy over 10 yr, while Lewis found observation’s quality. Spectra are taken IR star color “mimics” need explanation. that it then dropped to < 10 mJy in the with an 0.39-MHz total bandwidth, giv- Lewis has found that mimics are a man- following six months. Likewise, the OH ing a 0.14-kms-1 resolution at the OH datory feature of the transient-shell par- masers in VY Her have decreased by a lines. Moreover, the digital filters de- adigm, in which a superwind only factor of >10 and disappeared. Howev- fining the narrower correlator band- endures for ~500 yr after a He-shell er, the most spectacular changes are widths provide very smooth bandpasses. flash, while the extra “flash” luminosity those exhibited by 19566+3423, (see Our experience shows that observations causes the star to expand, thereby in- Fig. 7). Ten years ago this had a rather of strong (>50 mJy) features need no creasing its period and mass-loss rate. unusual 1612-MHz spectrum, prompting comparison OFF-source spectra, nor is The gas density in the circumstellar shell its early reobservation. While the factor observation confined to nighttime by then rises past the threshold that allows of three increase in 1612-MHz intensity baseline ripples; good observations can dust to couple photon momentum to it, is dwarfed by the factor of 30 increase be secured at midday. About 25% of with an immediate increase in its expan- in 1665-MHz intensity, unprecedented Arecibo OH/IR stars have been reob- sion velocity. Since a newly accelerat- changes in the velocity range of its emis- served to date, including all high-latitude ed shell quickly moves beyond its sion have been observed. This has ex- stars. dust-shroud, its molecules are rapidly panded from 16 to 42 kms-1 in the degraded by interstellar UV. Hence the An extra stimulus is lent to this 1612-MHz line, and at 1667 MHz from mimics. The subsequent acquisition of project though, by the new transient shell 28 to 80 kms-1. It is presumably a super- masers by a mimic shows that its super- scenario. This expects the duration of giant or hypergiant star with a rapidly wind has long climaxed, and that a pro- the superwind supplying the dense shells evolving circumstellar shell that may tective dust-shroud from the current hosting 1612-MHz masers to be rather well have been lost in a sudden mass expansion is again extending the longev- ejection event, rather than in a wind. Its

October 1999, Number 28 7 NAIC/AO Newsletter tire 8-year data set, is 30 yr ago. They are developing an oper- 19586+3637 shown as a solid curve. ation mode of the 168-MHz bandwidth 300 1612 MHz Since the amplitude of a Berkeley-Arecibo-Caltech Swift Pulsar propagation-induced peri- Instrument (BACSPIN) that can deliver 200 odicity would have to dedispersed time series of power in or- 100 scale as λ2, it should be thogonally polarized channels (single or Flux ( mJy ) entirely invisible at 1130 subbands) and will soon have full Stokes 0 µ -20 0 2 0 4 0 MHz given a ~4 s tim- parameter capability. Any observers in- LSR Velocity ( km/sec ) ing precision at that fre- terested in using BACSPIN are encour- quency. Consequently, aged to contact Don Backer. Fig. 8: The 1612-MHz, OH-maser emission spectrum of 19586+3637, this result adds to the evi- Duncan Lorimer, Fernando Camilo on 29 May 1999. (Courtesy Murray Lewis) dence in favor of a Moon- (Jodrell Bank/Colombia) & Kiriaki Xil- mass, 25.3-day orbit ouris have begun a timing campaign on companion to PSR B1257+12 and ity of molecules. 19586+3637, (alias 17 pulsars discovered over 25 years ago proves that this periodicity cannot be V1511 Cyg = IRC+40371), is a mimic by Hulse & Taylor during their survey induced by a propagation effect as pos- from Arecibo searches of 1988 and 1991 of the Galactic plane. The Hulse-Taylor tulated by Scherer et al. (and an earlier search at Nançay). On survey is most remembered for its dis- 29 May 1999, Lewis found this star to Don Backer & Andrea Somer (UC covery of the binary pulsar, B1913+16, exhibit a 300-mJy 1612-MHz maser (see Berkeley) have begun to investigate “or- which Joe Taylor and collaborators have Fig. 8); a mimic that has recently become thogonal mode emission” from pulsars used as a Gravitational Laboratory for an OH/IR star. — a phenomenon known for many the last 20 yr. Probably as a result of years, where it appears that two modes this, very little is known about the re- of orthogonally or quasi-orthogonally maining pulsars. It is hoped that the new Pulsars polarized emission are competing in pul- series of measurements will yield some Alex Wolszczan, Ian Hoffman & Maciej sar magnetospheres. The net result is a surprises about the remaining pulsars Konacki (Penn State) and Kiriaki Xil- randomization of the integrated polariza- from this survey. ouris (NAIC/NRAO) have conducted tion position angle. In order to study Andy Fruchter (STScI), Kiriaki Xil- multi-frequency timing observations of the implications of this phenomenon on ouris, Duncan Lorimer, Jo Ann Eder & the planet pulsar, PSR B1257+12. Mea- the emission mechanism, Backer and Angel Vázquez (NAIC) have confirmed surements were made on a daily basis Somer aim to measure the extent to six more pulsars from the STScI/NAIC between May 5 and June 6, 1999, at 430, which the two competing modes each drift-scan search. PSRs J0137+16, 611.5, 1130 and 1410 MHz, using the follow the “rotating vector model” pro- J1549+21, J1822+11, J1838+16, Penn State Pulsar Machine (PSPM). The posed by Radhakrishnan & Cooke some purpose of this project was to investi- J1849+06 and J2040+16 are all slow, gate the claim published in 1997 by K. low-luminosity pulsars with Scherer et al. (Science, 278, 1919) that periods ranging between 0.4 a 25.3-day periodicity seen in the tim- and 2.2 sec, bringing the to- ing residuals of the pulsar is caused by a tal number of pulsars result- propagation effect in the interplanetary ing from the STScI/NAIC plasma induced by solar rotation, rather drift-scan search to nine. than being due to orbital motion of a Kiriaki Xilouris & Dun- Moon-sized planet (planet A), orbiting can Lorimer have been reg- the pulsar with the same periodicity. The ularly monitoring the highest quality data, obtained at 430 and polarization properties of 1130 MHz, are shown in Fig. 9 in the millisecond pulsars in glob- form of the best-fit residuals for a two- ular clusters, aiming at con- planet timing model including planets B trasting their properties with and C and ignoring the inner planet A those of field millisecond Fig. 9: Multi-frequency timing observations of the planet pulsar, PSR and its 25.3-day orbit. Clearly, both the pulsars. Preliminary polari- B1257+12, at 430 and 1130 MHz in the form of the best-fit residuals 430- and 1130-MHz data (shown as open metric profiles resulting from and filled circles, respectively) exhibit a for a two-planet timing model including planets B and C, but ignoring the inner planet A and its 25.3-day orbit. The 430- and 1130-MHz long integrations with the 25-day periodicity with approximately residuals are shown as open and filled circles respectively, and exhibit Arecibo Berkeley Pulsar Pro- µ the same ~3.5 s amplitude. The best- a 25-day periodicity with approximately the same ~3.5 µs amplitude. cessor (ABPP) seem to indi- fit model for planet A, based on the en- (Courtesy Alex Wolszczan)

October 1999, Number 28 8 NAIC/AO Newsletter cate that the brightest pulsars in M15 exhibit very little polarization, unlike normal pulsars, but similar to field mil- lisecond pulsars. The Princeton pulsar search collab- oration (Walter Brisken, David Nice, Kiriaki Xilouris, Steve Thorsett, & Fernando Camilo) made follow-up ob- servations based on pulsar search data taken with the PSPM during the upgrade. Three new pulsars (J1829+14, J2055+21, and J2227+30) were con- firmed, each with period slightly under Intensity (arb. units) one second. These pulsars were discov- ered in data covering roughly 600 square degrees of sky. Twenty known pulsars (including three recycled pulsars) were also redetected blindly in this data.

Bill Sisk, Jeff Hagen & Andy Dowd 0 20 (NAIC) have made excellent progress on Seconds implementing WAPP – the Wide-band Arecibo Pulsar Processor. This instru- ment uses an existing board that was Fig. 10: The first pulses successfully recorded by the Wide-band Arecibo Pulsar Processor (WAPP). The developed for the AO spectral-line corr- pulsar being observed was PSR B1541+09. (Courtesy Duncan Lorimer) elator. To manage the processing load, a Linux-PC performs post-processing both the HALCA orbiting antenna and and data storage. This combination gives clude wider band modes (adding more the Noto 32-m dish. Of the other exper- wideband performance (100-MHz band- 100-MHz units) and narrower band iments, 19 were observed for the Deep widths), with good time and frequency modes suitable for low-frequency work. Interferometric VSOP-Arecibo Survey resolution (64 lags every 64 µs). Larger (DIVAS) of weak AGNs by Hirabayashi numbers of lags may be possible for ap- (ISAS, Japan), Ulvestad (NRAO) and VLBI propriately longer sampling times (e.g. collaborators, and 4 for the VSOP 5-GHz 128 lags every 128 µs, etc.) Since much The terrestrial, 18-cm wavelength, VLBI flat-spectrum, bright AGN survey pro- of the processing is handled in the Linux- test experiment, INTAS98.5, organized gram. Fringes have been detected in all PC, it is quite flexible. It can support a by Molotov, Likhachev & Chuprikov cases but three, which await correlation. large number of modes including full (Astro Space Center) and observed on 2 polarization measurements. The difficult Dec. 1998, has now been correlated at the S2 correlator at Penticton, Canada. job of rapidly reading the correlation Zeeman Splitting of 21-cm Absorp- functions has been done and, during a Between Arecibo and the Green Bank tion Lines: A Surprising Result 140-ft telescope, signal-to-noise ratios of test run in late August, the first pulses Carl Heiles from B1541+09 were successfully re- about 37:1 were measured on both of the corded by WAPP (see Fig. 10). Present- pulsars, PSRs 0950+08 and 1133+16, This Spring we performed a preliminary ly, work is in progress to implement and with SNRs of 211:1 being registered for survey of Zeeman splitting of the 21-cm test the required modes and converting the quasar, B1156+295. line in absorption against nine extraga- lactic continuum sources. We used the the development unit into a working sys- Arecibo has participated in twenty L-wide feed and the correlator in “Stokes tem. The current plan is that WAPP will four 5-GHz observations in support of mode’’, which provides all four Stokes be available for use as a 100-MHz the Japanese-led VSOP Space-VLBI parameters. We thoroughly investigat- search/polarimetry machine by the pul- mission. So far in 1999, the targets have ed the polarization properties and docu- sar community by February 2000 and, all been quasars. In an experiment pro- mented the results in two Arecibo as such, observing proposals to use the posed by Garrett (JIVE) & Patnaik (MPI- Observatory Technical Memos. The L- system were actively encouraged for the fR, Bonn), fringes were detected on the wide feed is ideal for polarization work, October 1999 deadline. Future enhance- small separation, gravitational-lens can- ments to WAPP presently envisaged in- didate, J0226+343, between Arecibo and

October 1999, Number 28 9 NAIC/AO Newsletter because we associate or negative, it can mimic noise and with- high density with out a least squares fit one cannot get a low temperatures, reliable estimate for either the field or also with the 21-cm τ its uncertainty. The “signal” is the up- line opacity . Simi- and down-going peaks in Stokes V on larly, we expect ab- the left and right sides of the deep ab- sorption-line fields sorption line. Even though the fit has to be stronger than high formal significance, the eyeball is |B| ( Gauss) typical emission-line not impressed. Nevertheless, the detec- fields. However, no tion of B = 3.1 ± 0.5 µυG is certainly such trends are ob- real. served. In Figure 11, the high-field results One straightfor- are of great potential interest — if they ward explanation of Fractional Absorption are confirmed by more observations. this result is the fol- They all have large errors because the lowing, which is a absorption lines are weak. If they are -t Fig. 11: |B| versus fraction absorption (1 - e ) for the 21-cm line in absorp- big departure from real, then magnetic pressures amount to tion against 9 continuum sources. Error bars are 1σ. current astronomical the equivalent of thermal gas pressures thinking: (1) Cold P/k ∼ 4×105 cm-3 K, a full order of mag- clouds have high having cross-coupling terms well under nitude larger than typical thermal gas densities. (2) Condensation of a cloud 1%. pressures. The presence of such large to high density is inhibited by the mag- fields in weak HI absorption components Surprisingly, until our successful netic field. (3) Therefore, only regions would revolutionize our understanding Zeeman-splitting Arecibo observations in which the field is low can condense; of diffuse interstellar clouds. of last Spring, there existed only two regions with high fields must remain rar- sources with such measurements: Tau A, efied. In short, cold, dense regions au- B ~ 3 µG; and Cas A, B ~ 10 µG for the tomatically select just those regions that, two broad “Perseus arm” features and B before condensation, had low magnetic < 0.6 µG for the narrow “Orion Arm” fields. feature. Our survey greatly increases Each datapoint in Figure 11 is the these statistics, and moreover provides result of a long integration. Figure 12 the first absorption detections away from exhibits the data and the least-squares the Galactic plane. fit for 3C409, Our nine sources sample a variety of which has one of HI regions, with optical depths in the the best detections VLSR (km/s) range τ = 0.08→2.4, and avoid molecu- in our sample. The lar clouds. Figure 11 exhibits the results; thick line is the error bars are 1σ. They divide neatly Stokes V spectrum into two groups, “high” and “low” fields. and the thin solid The low-field results are low indeed, line the least- with 7 out of 8 having B < 2 µG and, squares fit to the σ Ι also, B < 2 B so that they are better de- Stokes V and scribed as upper limits. The low-field spectra for the val- Fractional Stokes I group has far weaker fields than HI emis- ue of magnetic field Stokes V (Kelvins) indicated. The sig- sion lines, which often exhibit B >5µG; ~ nature of Zeeman the emission lines sample warmer and, splitting is the ap- presumably, less dense gas. pearance, in the V Channels spectrum, of the This is a very surprising result. The derivative of the Ι Fig. 12: Data for a 10.4-hour integration on 3C409. The heavy solid line is current ideas about interstellar magnet- spectrum. Because Stokes V and the dotted line is Stokes Ι. Lighter solid line is least squares fit to ic fields lead one to expect an increase the derivative can Stokes V and I for the indicated field strength and channel range, which covers in field strength with volume density, and the deep line component. go either positive

October 1999, Number 28 10 NAIC/AO Newsletter cy as rapidly as ±1 Hz/s. Any signals on the precise position of the signal. This SETI Observations at Arecibo: Fall that are detected are compared against a has only happened a few times, and 1998 and Spring 1999 database of all signals seen thus far, when needless to say it has gotten our atten- Jill Tarter (SETI Institute) pointing the telescope in other directions. tion every time! The more usual se- Our first run ended prematurely thanks If they match, they are labeled as inter- quence of events is that having failed to to Hurricane Georges (in Sept. 1998), ference (entering through the sidelobes) detect the signal during the “OFF” ob- and the second run was challenged by and ignored. If they don’t match, they servation, it is also not detected on the the disintegration of a bearing on the are labeled as candidates and passed to subsequent “ON” observation. From Lovell Telescope at NRAL, Jodrell the FUDDs for the third stage in the pipe- noise alone we expect such false posi- Bank, so we are looking forward to the line. The FUDDs at both sites re-observe tives approximately once every thousand third time (November 1999) being a the target star at frequencies surround- candidate signals. In fact, our current charm! What does the Lovell Telescope ing the candidate signals. The main false positive rate is more like 1 in 143. have to do with this, isn’t this a report FUDD (at Arecibo) then analyses that This is the result of interference; either about Arecibo? Yes it is, but Project data with a series of FFTs (resolutions interference at Jodrell “confirming” a Phoenix routinely observes with two as fine as 0.01 Hz) to attempt to make a noise event at Arecibo, or temporally widely separated telescopes in order to coherent detection of the candidate sig- variable RFI at Arecibo being confirmed help discriminate against terrestrial in- nal at a higher SNR than the original by a noise event at Jodrell Bank. We are terference. When your main site is as power detection provided. If the Areci- currently looking at ways to drive this big as Arecibo, your remote site needs bo FUDD fails to find the candidate sig- rate down (in order to make our obser- to be as big as possible, hence the 76-m nal, it is labeled as noise and the vations more efficient). It would help if Lovell Telescope. Here’s what we do. observations continue (we set our thresh- we avoided the satellite bands, but we old so that noise alone will cause a few are unwilling to give up that much spec- Our goal is to observe 1000 nearby signal detections during every observa- trum without some additional applica- solar-type stars over the frequency range tion). If the signal is seen again, the tion of advanced cleverness in the form from 1 to 3 GHz; a systematic look at FUDD at Jodrell is polled to see if it also of frequency-specific masking of indi- our immediate galactic neighborhood. detected that signal with the precisely vidual spectral sub-bands (whose width To date, using the Parkes and Mopra an- predicted Doppler offset in frequency is about 1 kHz). The November 1999 tennas of the ATNF, and the 140-ft at and drift rate corresponding to the direc- run will tell us whether we’ve been clev- NRAO combined with a 30-m antenna tion of the target star, and with the prop- er enough. at Woodbury, GA, we have observed er ratio of SNRs for the different The bottom line is that we have not about 400 of our target stars. That leaves sensitivities at the two sites. A confir- detected any extraterrestrial signals from 600 stars for Arecibo. mation by the Jodrell Bank FUDD caus- the vicinity of the 96 stars we’ve looked es the TSS to abandon all data collection At Arecibo, we have installed a Tar- at so far, and we’ve satisfied ourselves and signal processing that has been in- geted Search System (the TSS sits in a that all the promising candidate signals progress in the pipeline, and to schedule trailer outside the control room) that we investigated had their (often un- both telescopes to move “OFF source” analyses 28 million channels of data known) origins in terrestrial engineering. for the next observation. If the signal is (0.67-Hz resolution) covering 20 MHz The sensitivity limit we currently detected by the TSS or the FUDDs dur- of spectrum, replicated to cover both cir- achieve is 8×10-27 W/m2, which corre- ing the “OFF” observation, it is classi- cular polarizations. We also use Follow sponds to a transmitter with an EIRP of fied as interference, and the TSS returns Up Detection Devices (FUDDs) at both 2×1011 W at the 155 light year distance the telescope to the target star to restart Arecibo and Jodrell Bank. These are of our most distant target star – equiva- the in-progress observations that had smaller detectors, capable of re-observ- lent to the power of terrestrial radars. been aborted. If however, the signal is ing interesting candidate signals discov- Because the surface accuracy of the Lov- not seen at all in the “OFF” observation, ered by the TSS. The signal detection ell telescope is inadequate for 3-GHz then the TSS again returns to the target and follow up are accomplished in near- observations, we’ve restricted ourselves star and tries to reacquire the signal. If real-time with a three-stage pipeline. to L-band observations thus far. An up- the signal is found once again, bells ring, First, the data are collected at Arecibo, grade of the Lovell surface should per- and cell phones get dialed to alert sleepy transformed into spectral channels, and mit S-band observations within a year. stored. Next the stored data are exam- observers and those off-duty that a very ined for patterns in frequency and time interesting candidate signal is being ex- The one exception to this frequency that would indicate a narrow-band CW plored. Until humans intervene, the TSS rule is the daily observations we make signal or a narrow-band pulse, even if is programmed to continue to observe of the Pioneer 10 (P10) spacecraft at these signals are changing their frequen- “ON” and “OFF” source and to execute 2295 MHz. We have constructed an in- a grid of observations to try to peak up terim, uncooled, S-band receiver for the

October 1999, Number 28 11 NAIC/AO Newsletter Lovell telescope that is mounted next to proof. I suspect that we the standard L-band receiver at the prime are over the worst of the focus. At Arecibo we use the S-band teething problems associ- Narrow receiver, with its internal filter ated with a new program removed to permit tuning to the space- of observations. I look craft frequency. This allows us sufficient forward to a smooth run sensitivity to detect P10. Fig. 13 shows in November. Once we the detection of the sideband and carrier have achieved that goal, from P10 using the NRAO 140-ft, and we will begin to explore Fig. 14 shows the P10 sideband detect- the possibility of control- ed by Arecibo. This spacecraft has left ling both Arecibo and Jo- the solar system behind, and has only a drell Bank remotely from 6-W transmitter, so it serves as a good an observing console in example of what an extraterrestrial sig- Mountain View, CA. nal from a distant star might look like. Rest assured, in the spirit Our daily system test requires that the Fig. 13 - The P10 Sideband and Carrier detected with the NRAO 140-ft of planning for success telescope. TSS finds the signal, and the FUDDs that causes us to keep confirm it, in order to verify that all sig- champagne on ice, we nal processing hardware and software shall certainly send one scientist to Areci- and Jodrell. Pulsar observations finally components are fully functional. When bo even if we observe remotely. There unraveled the confusion, and we re- this spacecraft finally loses lock on the is no telling when silicon-based intelli- versed the connectivity at Arecibo. Cop- Earth and its signal gets too faint, we will gence will turn up something that needs ies of the Arecibo helical transmitters have to resort to nearby spacecraft, and to be explored by carbon-based intelli- have now been manufactured by Eddie insert an extra piece of code to do these gence. Castro and the electronics shop and sent daily system tests. to Jodrell Bank – next time we’ll mea- In addition to the hurricane and bro- sure the polarization directly. To say ken bearing, our observing campaigns thank you for this and all of the other Space and Atmospheric Sciences have traversed some other bumps in the extra effort that the Arecibo staff have Craig Tepley and Mike Sulzer road. A dedicated frame relay that was expended on our behalf, we had a party Experimental studies since last March intended to link Jodrell Bank and Areci- during our spring campaign and gave out were numerous. The Wide Latitude bo was delayed in installation until the groovy Phoenix T-shirts. Jill began to Storm (WLS) coverage World Day ex- spring of 1999 run – we used a dial-up learn the Danza, and maybe some local periment scheduled for 20-22 April start- modem in the fall. Data occasionally got folks picked up a little samba. If hard- ed on time, but we had to end this study lost, and you don’t even want to think ships lead to such nice parties, maybe early due to a serious problem encoun- about the phone bill! Our custom digi- we should pencil in more hardships. :) tered with the 430 MHz transmitter. This tal signal processing equipment is pret- We have made a ty intolerant of voltage fluctuations on lot of progress, despite the power lines supplying it. A flywheel the bumps in the road. rotary UPS was ordered. Delayed in Over two thousand completion, delayed again by Hurricane observations of 96 Georges, it arrived at the Observatory stars, each lasting 276 damaged beyond use. It is now back in sec, and covering 20 California being repaired, and will hope- MHz of the L-band fully be installed safe and sound for our spectrum have been next campaign in November. Mean- completed. The soft- while, we have had to rent a diesel gener- ware interface with ator and impose upon observatory staff Jodrell Bank for an- for help in maintaining it and protecting tenna control has sta- it from Georges. The first 2.5 days of bilized, the interface the spring observations were compro- to Arecibo has not, but mised because wires got switched at staff at AO and SI are some unknown instant, and we had a po- working together to larization mismatch between Arecibo Fig. 14 - The P10 Sideband detected at Arecibo Observatory make this more bullet-

October 1999, Number 28 12 NAIC/AO Newsletter The New Space and Atmospheric Sciences Program Don Campbell and Paul Goldsmith Over the past year, there have been discussions within NAIC, and between NAIC and the NSF, concerning a reorgani- zation of the Atmospheric Sciences Program. The outcome was the decision to appoint an Assistant Director of NAIC for Space and Atmospheric Sciences, with the change in name recognizing the changing emphasis of the Program. After an extensive search, Don Farley, Professor of Electrical Engineering at Cornell University, has been appointed as the new Assistant Director. Don is a world recognized expert in the application of incoherent scatter radar techniques to the study of the earth’s ionosphere. He will continue to reside in Ithaca but will make frequent trips to the Observa- tory. Don will be responsible for the Observatory’s research program in space and atmospheric sciences and will be NAIC’s primary contact person with the Upper Atmosphere Facilities section of the NSF Division of Atmospheric Sciences The organization of the Space and Atmospheric Sciences program at the Observatory has also been changed. Pre- viously, there were two departments, Atmospheric Sciences headed by Dr. Craig Tepley, and Ionospheric Modification headed by Dr. Michael Sulzer. Under the new arrangement, Craig Tepley will head the Optical Sciences Department in Space and Atmospheric Sciences, and Mike Sulzer will head the Radar Sciences Department. Mike will continue to be responsible for the planning for a future ionospheric modification capability. Craig and Mike are two of the nation’s foremost experts in their respective fields and will provide the leadership to keep Arecibo at the cutting edge of optical and radar studies of the Earth’s atmosphere.

particular experiment was designed to bo, we ran this experiment in shifts During the daytime of 31 July, and study how a geomagnetic storm might where Bryan MacPherson, Nestor Apon- again on 1 and 8 of August, Qihou Zhou affect the ionosphere. All incoherent te, Sixto González, and Qihou Zhou (all and Mike Sulzer (NAIC) obtained many scatter radars and a number of optical of NAIC) took turns to answer questions excellent spectra from the D-region and facilities, in the US, South America, and from the public at the “ask a scientist” lower E-region ionosphere using the 430 in Europe, participated in WLS. For part of the SPARC web-pages. MHz incoherent scatter radar (ISR). WLS we ran the 430 MHz radar in a con- With the optics, we ran for eight From these spectra they were able to tinuous beamswinging mode to measure nights (~72 hrs total) centered on the determine the neutral winds in order to plasma drifts, electron concentration, April WLS, obtaining Fabry-Perot inter- compare with those winds obtained by and temperatures. At night we also ob- ferometer (FPI) observations of O(1D) the 1.95 MHz MF radar located near served thermospheric winds and Hα in- 630.0 nm winds and exospheric Hα Aguadilla, PR, and operated by Mario tensities with our optical instruments. emission lineshape measurements, using Ierkic and Héctor Monroy (UPR-May- Despite the problems mentioned, we our two facility FPIs. We also used two agüez). Both ISR and MF radars ran well were able to contribute to most of the of our tilting-filter photometers to ob- for these three daytime periods, except WLS period, obtaining quality informa- serve Hα and the atomic oxygen triplet for some minor interruptions caused by tion on the upper atmosphere, which at 844.6 nm, the latter of which origi- lightning and other radar interference. should compare well with those data nates in the F-region ionosphere. To collected at other sites worldwide. With the ISR, Zhou and Sulzer ran obtain information at lower altitudes, we three observing programs, that is, a D- The April 48-hour core period of used our spectrometer to measure the region pulse-to-pulse FFT, an E-region WLS was originally set up to “float” OH(6-2) and O2(0-1) near-infrared emis- coded long pulse (with a 400 µs pulse; within a month-long window to maxi- sion bands from which we derive the 50 baud), and the power profile program. mize the chances of observing the onset neutral temperature of the lower thermo- The first data taking program resulted in of a storm. Unfortunately, the magnetic sphere. Additional nights of 630.0 nm winds up to about 90 km altitude while activity was less than moderate and the wind observations were made through- the second program measured ion drifts dates for the run were fixed on their de- out the summer and will be analyzed and from 90 km to about 170 km. Finally, fault core period. WLS was part of the submitted to the CEDAR Database for with the last program they measured the Space Physics Atmospheric Research use by the general aeronomy communi- electron concentration from 60 km to Collaboratorium (SPARC) where real- ty. about 550 km. The ISR was mainly time data were commonly viewed by all pointed to the west and slightly north- participants via the internet. At Areci- ward on 31 July and 1 August, but on

October 1999, Number 28 13 NAIC/AO Newsletter the 8th it was pointed in four cardinal di- proved system by the end of the year. termination of neutral winds from the rections with the hope that this new com- While it is at the factory, we are taking same altitude region that we can now parison will resolve some of the advantage and having the dye laser ret- measure the temperature. long-standing issues concerning the va- rofitted for an option to allow observa- In a significant area of improvement lidity of the winds determined with the tions at other wavelengths, particularly with regard to the backlog of optical data MF radar technique. within the blue part of the optical spec- that has been collected at Arecibo, we trum. This change will permit us to ob- Another WLS World Day study took are pleased to report that Eva Robles serve the resonance lines of other place in September, but this time mag- (NAIC) has made considerable progress prominent metallic species found in me- netic conditions were more conducive to analyzing many years of 630.0 nm FPI teors, such as Fe, Ca, and Ca+, and ex- storm activity. The 48-hour core period observations, and has nearly brought us amine their altitude distributions within was originally scheduled for 7-9 Septem- up to date with the processing. Before the mesopause region of the upper at- ber, however, predictive magnetic con- the CEDAR meeting this summer, we mosphere. ditions based on the level of solar activity submitted to the CEDAR Database 160 made it necessary to “float” these core Although the Nd:YAG/Dye laser sys- nights of observations, which doubled days a week later to 15-17 September. tems were temporarily removed from the amount of neutral wind data from This, in turn, required us to reschedule service, Jonathan Friedman (NAIC) car- Arecibo that had previously existed in several radio astronomy experiments, ried out potassium density observations the Database. Only data up through 1998 plus a study to observe main-belt aster- as part of the process of optimizing the were submitted, but we do have a few oids. It was very fortunate that we were alexandrite ring laser for wind and tem- gaps to fill in from the past few years, able to work out the details of the sched- perature measurements. During the pe- and need to work on the data from 1999. ule to everyone’s satisfaction. As a re- riod of 12-20 July, the system was run We expect to be fully caught up within sult, we had a successful WLS study at night whenever the weather permit- the next couple of months, but we sent where we were able to observe several ted. Later, we suffered a power outage what we had to date before the CEDAR interesting storm related features. Our in the lab followed by unstable power meeting so this community can begin to radar and optical instrumentation per- conditions during the week of 9 August, work with the results. After we are up to formed very well for this experiment. which unfortunately included the peri- date with the wind data, we will also sub- od of peak activity of the Perseids mete- mit to the Database the 20+ years of in- Preceding the September WLS study or shower. However, we were back on tensity data collected using the was a similar experiment conducted by the air by the night of 16 August when photometers at Arecibo. Plus, we intend Mike Kelley (Cornell) and Nestor Apon- potassium density observations re- to submit our derivations of mesospher- te. Roughly a week of radar and optical sumed. An example of potassium den- ic temperatures and band intensities ob- observations were made to examine the sity observations, from 7-8 September, tained by observing the OH and O irregular structure of the F-region iono- 2 is shown in Figure 15. rotational emissions (mentioned previ- sphere during periods of quiet and in- ously), which we have collected since creased magnetic activity leading up to Throughout August and September about 1985 when this part of our optical a storm. Mercedes Huaman, an EE post- the potassium lidar was configured for observation program began. doc, was on site during this experiment our first mesospheric temperature mea- to work with the Cornell imager as well surements at Arecibo using the lidar Most members of the Atmospheric as our own instrumentation. Several technique. This involved using an Sciences Department at Arecibo partici- good nights of simultaneous radar and acousto-optic modulator to shift the pated in this year’s annual CEDAR optical data were obtained, which transmitted laser frequency about the Meeting held in Boulder, CO during 14- showed some interesting long-period center frequency of the potassium reso- 18 June. Relevant highlights of that wave features in the O(1D) 630.0 nm air- nance line. The ratio of the backscat- meeting included a plenary science talk glow and related plasma drifts. tered signal off the K resonance center by Mike Sulzer on the effects of elec- frequency to that on center allows us to tron coulomb collisions on incoherent In news concerning the Lidar Labo- determine the temperature. Preliminary scatter spectra, a workshop on the Top- ratory, the Nd:YAG laser system that we results are shown in Figure 16, where it side Ionosphere co-chaired by Sixto generally use for Rayleigh lidar studies is clear that a minimum in the ratio (cor- González, John Noto (Scientific Solu- of the middle atmosphere, and as a pump responding to the temperature mini- tions, Inc.), and Phil Ericson (Millstone laser for the resonance lidar density mea- mum), the so-called mesopause, is Hill Observatory), a sub-session on surements of sodium in the upper atmo- evident near 90 km. The process to con- Arecibo capabilities (chaired by Craig sphere, has been out for repairs at the vert to temperature is complex and un- Tepley) during the general Incoherent factory since the end of March. We are derway at this time. Further refinements Scatter Radar Facilities workshop, and expecting the delivery of a new and im- to this lidar system will allow for the de- our participation in the discussions on the

October 1999, Number 28 14 NAIC/AO Newsletter 100 na University) also worked with J. Fried- Potassium Abundance (cm Potassium Abundance 105 man to refine the diagnostics that we use 75 100 for maintaining the transmitter for the K Doppler-resonance lidar. Finally, Miguel 95 50 Ruiz (University of Puerto Rico at May- 90 agüez) supervised by Edgar Castro of our

Altitude [km] 85 25 Electronics Department (together with J. -3

80 ) Friedman) did a project that involved the 0 8.0×107 re-design and construction of a gate de- lay circuit used during lidar observations. ]

-2 Overall, the REU students had a chal- 6.0×107 lenging, yet very productive summer at Arecibo.

× 7 4.0 10 In June, the adjustment of the plat- form height in June improved our sensi- 2.0×107 tivity, and this was soon reflected in the results of World Day observations. In

Potassium Column Abundance [cm Potassium Column October we had two campaigns, a Low- 0 23 00 01 02 03 04 05 er Thermosphere Coupling Campaign Local Time (LTCS) which began on October 12 and a POLITE (topside ionosphere) cam- Fig. 15: Mesopause potassium concentration (above) and column abundance (below) as measured with the paign, which ran on October 8 and 9, and Arecibo Observatory Doppler-resonance lidar during the night of 7-8 September, 1999. (Courtesy Jonathan had an extra night due to an observing Friedman) proposal by Robert Kerr (Scientific So- lutions, Inc.). This experiment had a par- ticularly gratifying result: it is the first 100 Coquí-II rocket campaign at a workshop October since the last solar cycle with chaired by Miguel Larsen (Clemson). conditions approaching solar max, and This last workshop included making we were expecting large numbers of plans to write several follow-up papers Helium ions. The Helium ion fraction based on the campaign results. We have 95 in an early morning layer did approach already published a set of preliminary 40% as we were hoping. Thus our des- papers in a special issue of Geophysical ignation of October as the IHM (Inter- Research Letters (to appear later this national Helium Month) remains valid. year), but further papers will describe the 90 data collected during Coqui-II and its The experiments discussed below use either high resolution ion line or plasma Altitude (km) analysis in greater detail. line techniques, or both, rather than the This summer we hosted a number of standard techniques that experiments 85 excellent REU Summer Students, four such as the World Day and Topside use. of whom worked with atmospheric sci- These experiments show the exception- ences staff members. Lily Childress al capabilities of the Arecibo radar. In (Harvard) worked with Mike Sulzer and the next year our ability to make high 80 her “remote advisor”, Colin Hines (York resolution plasma line measurements 0.5 1.0 AOM on University), to solve a set of equations will be extended by the completion of Ratio ( AOM off ) related to the spectral distribution of at- the dual-feed transmitting capability. mospheric gravity waves. Ameet Kini The wider bandwidth of the Gregorian Fig. 16: Preliminary results from the Arecibo Dop- (University of Maryland) did a multifac- feed will allow the use of plasma fre- pler-resonance lidar. The ratio (AOM on / AOM off) eted computer programming project for quencies encountered near the peak of is approximately proportional to the temperature. Eva Robles, Jonathan Friedman, and the F region. The actual temperature value is gained from precise Craig Tepley, which involved interactive knowledge of the potassium spectrum. (Courtesy optical data analysis and visualization, E-REGION TEMPERATURE MEASUREMENTS: Stephen Collins) web display, and data collection, respec- An experiment was carried out in Janu- tively. Keith Nowicki (Northern Arizo- ary by Silvia Duhau (U. of Buenos Aires)

October 1999, Number 28 15 NAIC/AO Newsletter with the goal of verifying measurements Te/Ti). Then the question is: Does this used as an input to the ion line fit, and of temperatures in the E-region made by profile match the one derived from the then the fact that the masses of O+ and sounding rockets. Rocket-borne instru- fit to the ion line spectrum in the alti- molecular ions are within a factor of two ments have shown that the electron tem- tude range near 130-140 km, where we is not an insurmountable problem. It ap- perature is significantly higher than the trust the ion line measurements? Figure pears that the molecular/O+ crossover

neutral temperature, at least under cer- 17 shows two profiles of Te/Ti versus al- height can be determined to less than a tain conditions in the E-region. ISR titude. The noisy gray lines are the data few kilometers, perhaps to within one ki-

measurements consistently show Te=Ti, with 300 meter resolution, and the black lometer. These results will be presented as determined from the ion line, but the lines are fifth order polynomial fits. The at the fall AGU. accuracy of these results at some alti- top plot shows one derived from the ion COLLISION MODELS: The second use for tudes depends upon knowing other quan- line; remember we trust it for sure in the these data is to determine the validity of tities independent of the radar 130-140 km range. The strange behav- the theoretical effect of collisional mod- measurements. For example, ion-neu- ior at the lower end of the altitude range els on the incoherent scatter spectrum. tral collisions become important below is due either to a bad collision model or If we assume for the moment that the about 125 km, and one must know the problems in the physics describing the BGK model, which is used by all of the height profile of the collision frequency effect of the collisions on the incoher- radars, gives accurate spectra at all col- accurately, or the accuracy of the T /T ent scatter spectrum. We discuss this be- e i lision frequencies, then the following measurement is affected. Also, the ef- low. The bottom plot shows a profile fect of the collisions on the incoherent derived from the plasma line

scatter spectrum must be known very and the ion line power pro- Date: 230199 From: 115048 To: 115718 + accurately. Above about 150 km, O ions file. It equals one at the low- 190

become significant and errors in the as- er heights by our calibration 180 sumed composition model affect the ac- of the ion line profile. If this 170 curacy of Te/Ti measurements. However, is correct, then the profile on in the 130-140 km range the result is very the bottom plot should have 160 reliable because it does not depend upon the same value in the 130- 150 either of these unknown quantities. That 140 km range as the profile

Height (km) 140 is, the effect of collisions is negligible, in the top plot. It does with- 130 and the ion composition is almost entire- in experimental error and From fit to ion line acf ly molecular. Thus the analysis is very since our only uncertainty 120 simple in this altitude range, and we can was a calibration at one 110 trust the T /T measurements. point, we conclude that the e i 100 entire profile in the bottom 0.8 1 1.2 1.4 1.6 1.8 Thus, we need additional informa- Temperature Ratio plot must be valid and there- tion; the Arecibo radar makes very ac- fore T does equal T at the curate, fast, high resolution plasma line e i lowest heights in this in- 190 measurements using the coded long stance. We conclude that this pulse technique. These very high-reso- 180 plasma line/ion line power lution measurements are not yet a stan- 170 comparison is a very power- dard, everyday capability because of the ful new tool for studying the 160 large amount of computation required. lower ionosphere, and will 150 We make these measurements by record- become much more so when 140

ing raw data, and the computing off-line Height (km) the processing can be done can take months. The ion line measure- 130 From plasma line in a reasonable amount of ments are made with the same coded and ion line power time. 120 long pulses, further increasing the com- 110 putational burden. COMPOSITION PROFILES: The discussion above suggests 100 The plasma line can give us accurate 0.8 1 1.2 1.4 1.6 1.8 two additional uses for these Temperature Ratio values of the electron density, but this data. First, since we have an alone does not give us T /T . However, e i independent profile of T /T Fig. 17: Two profiles of T /T versus altitude. The noisy gray lines are using an ion line power profile as well e i e i up to 190 km, we can mea- the data with 300 meter resolution, and the black lines are fifth order we can obtain a very accurate profile of sure the composition in the polynomial fits. The top profile is derived from the ion line. The T /T using the approximate relationship e i F1 region. The independent bottom plot shows a profile derived from the plasma line and the ion that the power is proportional to 1/(1 + line power profile. (Courtesy Mike Sulzer) measurement of Te/Ti can be

October 1999, Number 28 16 NAIC/AO Newsletter process should work. We assume that ing only the total power, the hole was quires a combination of good range, over the approximately 10-15 km where clearly seen, but an enhancement in back time, and frequency resolution. The only our data are sensitive to both collisions scatter power appeared near the edges way it can be done is to use the coded and temperatures, we can find a model of the hole. A possible explanation is long pulse with 150 meter range resolu- with an exponential height variation that the interaction with the exhaust heat- tion, even though this is at least 10 time which gives consistent results. That is, ed the ions, but not the electrons of better than required, and then average the

when Te and Ti are left free in the non- course, causing a decrease in Te/Ti, and independent samples in range to obtain linear least squares fit, we should find thus increasing the backscattered power sufficient accuracy with good enough

that the resulting Te and Ti really are perhaps even with a decrease in the elec- time resolution. The high signal to noise equal when using the correct collisional tron density. It is also possible that the ratio of the Arecibo radar means that the model. When we perform this process, ion velocity distribution has become measurements are clutter-limited, and so we find that there is no exponential col- non-Maxwellian, making the standard using a shorter-baud code and a wider lisional model that gives Te = Ti over this incoherent analysis invalid to some de- filter does not hurt the measurement at altitude range in the E-region. gree. each range, and so we want as many in- dependent ranges as possible. This is a disturbing result that must Thus the goal of this new experiment be explained. The work of Hagfors and was to observe the incoherent scatter The results of the experiment are Brockelman (1971) suggests the expla- spectrum rather just the total power. This shown in Figure 18. The top panel shows nation. They compared incoherent scat- is somewhat of a challenge since it re- the electron density calibrated to our dig- ter spectra using the BGK collisional model and a simplified model of hard body collisions. The results agree well Log of Ne (cc) vs. Ht (km) and Time beginning on 270799 for a large collision frequency, but not 5.968 for a small one. They suggested that this 300 5.691 discrepancy might have an effect on the 5.415 280 5.139 accuracy of the temperature measure- 4.862 missing data

ments. It is possible that we have found Altidude (km) 4.586 260 experimental evidence for this. Thus it 4.310 will be necessary to use their model in 4.033 our fitting program to see if we get bet- 0.8 0.85 0.9 0.95 1 1.05 ter results. If it is found that this better Ti vs. Ht (km) and Time beginning on 270799 collisional model is required, then it 1769 might be necessary to determine if their 300 1576 approximate solution is good enough. 1383 280 1190 This can be done by performing a digi- 998 tal simulation similar to the one per-

Altidude (km) 805 260 formed by Sulzer and González (NAIC) 612 for electron Coulomb collisions. These 419 predictions have not been fully verified 0.8 0.85 0.9 0.95 1 1.05 by experiment, and we would not expect Te vs. Ht (km) and Time beginning on 270799 ion neutral collisions to differ from sim- 1765 ple models. 300 1573 1381 SHUTTLE BURN: Our second highlight is 280 1189 an experiment which has been performed 997 806 before at Arecibo and at other incoher- Altidude (km) 260 missing data missing data ent scatter radars by Paul Bernhardt of 614 NRL. The space shuttle performs a small 422 0.8 0.85 0.9 0.95 1 1.05 engine burn in a pass as close as possi- Time (AST) ble to the radar beam, and the radar is Shuttle burn used to study the effects of the shuttle exhaust on the plasma. As expected, the Fig. 18: The effect of a Space Shuttle engine burn on the F-region as reflected in the 430 MHz incoherent primary effect is to cause rapid recom- scatter spectrum on July 27. The top panel shows the electron density calibrated to our digital ionosonde. The bination and thus form a hole in the F middle panel shows that the ion temperature increased at the instant of the burn. The bottom panel shows the region. In a previous experiment observ- electron temperature. Note that Te = Ti in the regions not affected by the shuttle burn. (Courtesy Mike Sulzer)

October 1999, Number 28 17 NAIC/AO Newsletter ital ionosonde; the densities are some- what higher than expected, but the post- midnight collapse has not yet occurred. The electron density decreases with the shuttle burn as expected. (The shuttle passed over at a height of 280 km.) The raw power profiles (not shown) show enhancement at the higher and lower heights, in agreement with previous re- sults, but the fitting to the spectrum shows that these enhancements are ap- parent only. The middle panel shows that the ion temperature increased, but this is not the full story. The bottom panel shows the electron temperature. Note

that Te = Ti in the regions not affected by the shuttle burn. The electron tempera- ture apparently decreased. This is not possible, but is the expected result of a non-Maxwellian velocity distribution. Bernhardt has a model for making these spectra and we will be further analyzing these data. The “spike” in all three pan- els at about 0.845 is presumably due to bad data, perhaps a strong meteor echo extended in range by the long coded pulse. A few similar, but weaker spikes are seen at later times. Fig. 19: The 1.5 km resolution radar image of the north polar region of Mercury obtained on July 25-26. (Courtesy John Harmon) The Planetary Radar Program Don Campbell Just prior to Hurricane Georges strik- observations of very nearby asteroids and ing Puerto Rico one year ago, the S-band comets with round-trip light travel times This year the planetary studies group at transmitter’s high voltage cable from the as small as 10 seconds, frequency the Observatory has been joined by two power supply on the ground to the trans- switched CW observations of near earth new staff members, Ellen Howell and mitter’s final amplifier in the Dome suf- and mainbelt asteroids, and planetary Jean-Luc Margot, bringing its total num- fered a catastrophic failure. These cables satellites such as Titan, and delay-Dop- ber to six. Most of the group combine are very specialized and it was not until pler mapping observations of Mercury their research activities with other obli- March that a temporary replacement ca- and Venus including interleaved point- gations to the observatory’s operations, ble was obtained that allowed the plan- ing measurements. Under development but for the first time in many years the etary radar system to resume operation. is software for pseudo-infinite length Observatory has a significantly sized Since then, the transmitter has worked phase coded observations of overspread group in planetary studies. Ellen, who is very reliably under the care of Tony Cre- targets such as the Galilean satellites of supported under her own grant from spo . The only problem was the loss in Jupiter, and for frequency switched de- NASA’s planetary astronomy program, September of a filament transformer in lay-Doppler observations of the rings of is interested in asteroidal compositions the socket tank of one of the transmit- Saturn. Most of these observations re- derived from optical/infrared spectros- ter’s amplifying klystrons resulting in quire integrated control of the transmit- copy and her work complements the ra- half power operation until it was repaired ter, the transmitter’s modulation, the dar observations of asteroids made at the in mid-October. Dome’s rotary floor, antenna pointing, observatory. Jean-Luc’s current interests data acquisition, Doppler correction, and, Significant improvements have been are in innovative techniques for imag- eventually, the telescope’s tie down sys- made, primarily by Phil Perillat, over the ing asteroids and other solar system bod- tem. ies with radar. past few months in the system control and data acquisition software. Included Data acquisition hardware for radar are new capabilities for delay-Doppler astronomy is being significantly en-

October 1999, Number 28 18 NAIC/AO Newsletter hanced by a new 20 MHz bandwidth di- rect sampling system being developed by Margot. A single channel prototype of the system has been taken to both the Madrid and Goldstone 70 m NASA/ DSN antennas to record data for tests of high resolution radar interferometric delay-Doppler mapping observations of asteroids. In these experiments, Areci- bo transmits and the echo is received by both Arecibo and the Madrid or Gold- stone antennas. The interferometric fringe phase is an additional input to the modeling of the asteroid’s size, shape and surface structure. Since May there have been observa- tions of Mercury, Venus, the three icy Galilean satellites of Jupiter and a num- ber of both near earth and main belt as- teroids. In July, John Harmon (NAIC) Fig. 20: The 15 m resolution delay-Doppler image of the near earth object JM8 obtained on August 5 as it and Martin Slade (JPL) continued their passed within 9 million km of the earth. (Courtesy Jean-Luc Margot) investigation of the probable water ice deposits at the poles of Mercury using component in the reflected signal would out CW and ranging observations of the the 2.38 GHz radar system with a range indicate penetration of the radar wave main belt asteroids 41 Daphne, 105 Ar- resolution of about 1.5 km. At this reso- into the surface, implying that sub-sur- temis, 198 Ampella, 85 Io, 219 Thusnel- lution the structure of the individual de- face scattering probably plays a role in da, and 216 Kleopatra in the continuing posits on the shadowed floors of the causing the high reflectivities. The ab- program for measuring the radio wave larger impact craters is very clearly de- sence of a linear component may indi- scattering properties of main belt objects. lineated and, somewhat unexpectedly, cate that the echo results from pure In June, Ostro, L. Benner (JPL), Camp- there appear to be ice deposits in small surface reflection, implying that the sur- bell, Giogini, Hudson, Nolan and Yeo- craters at significant distances from the face material has an intrinsically high mans obtained the highest resolution poles (Figure 19). Greg Black (NRAO), reflectivity. A careful search will also be delay-Doppler imaging of an asteroid to Don Campbell (NAIC) and Harmon also made for any surface changes since the date, 15 m, for the NEO 6489 Golevka. detected the ice deposits with the 430 Magellan mission related to volcanic Under a separate proposal, Margot and MHz radar system. Modeling based on activity, aeolian processes or landslides. Nolan attempted radar interferometric the 13 and 70 cm results will be used to delay-Doppler imaging observations uti- The study of asteroids, both those that derive constraints on the depth and oth- lizing the Arecibo and Madrid antennas. come close to the earth (NEOs) and those er properties of the ice. A detection of Golevka was made with in the main belt, is a major objective with Madrid but the signal-to-noise ratio was In August Campbell, Bruce Camp- the upgraded S-band radar system. Since not high enough to obtain fringes. bell (National Air and Space Museum), April, successful observations have been Margot, John Chandler (SAO) and Lynn made of six mainbelt asteroids and six In May of this year the NEO 1999 Carter (Cornell) made the first mapping NEOs. Four of the NEOs were only dis- JM8 was recovered and plans made for observations of Venus since prior to the covered shortly before their close ap- radar observations at both Arecibo and Magellan mission to that planet. These proaches to the earth and were observed Goldstone. JM8 passed within about 9 will complement the Magellan results by under proposals for targets of opportu- million kilometers of the earth and, at providing information on the polariza- nity. This worked well, with other ob- an estimated size of approximately 3 km tion properties of the reflected signal. A servers displaying considerable provided an excellent opportunity for major puzzle from previous radar and flexibility in rearranging their observa- high resolution imaging observations. At radio thermal observations of Venus is tions to allow for the radar work. Arecibo these took place over the first 9 the low emissivity and, hence, high re- days of August and involved the same C. Magri (Maine), M. Nolan (NAIC), flectivity of terrains at high altitudes. The group of observers as for the Golevka S. Ostro, J. Giorgini (JPL), R. Hudson polarization results may help to explain observations. Figure 20 shows the 15 m (WSU) and D. Yeomans (JPL) carried this phenomenon. A linearly polarized resolution delay-Doppler image obtained

October 1999, Number 28 19 NAIC/AO Newsletter on August 5. This image, when com- el) taken during construction. Together three miles of fiber optic cable needed bined with others made at different rota- this provided sufficient information to to establish this link, as part of the pack- tional longitudes, will provide a very adjust independently each of the four age, and this is indeed happening as I detailed three dimensional model of panel corners where they attach to the write. PRTC will also provide and in- JM8. connection plate. This work was carried stall the necessary termination equip- out in August. The resulting standard de- ment. viation is well below 1 mm rms. A few This major upgrade to the Observa- Secondary subreflector adjustment remaining large deviations near the edge tory communications infrastructure con- Mike Davis of the subreflector will be aligned in De- sists of a new T1-speed (1.544Mbits/s) cember, and a final survey made. Cut a tennis ball in half, pick it up by the link to the Internet, as well as a T1 voice edges and squeeze a bit. Our secondary The tertiary subreflector was also re- link for our telephone communications. reflector had this type of deformation measured, but found to be as accurate as The new switchboard, also provided by (astigmatism) following its lift to the when it was initially aligned on the PRTC, and still in need of final program- platform after alignment on the ground. ground. No further adjustments were re- ming adjustments, provides several ad- Though relatively mild, it could affect quired. Plans are under way for realign- vantages to our users, most importantly observations at the shorter wavelengths. ment of the primary reflector, which now the ability, at any time, to dial extensions dominates the Ruze Law losses by a directly and to leave voice mail. The fi- Donna Kubik, assisted by Tapasi large factor. ber-based link, routed directly via the Ghosh, Chris Salter, Mike Nolan and PRTC’s Arecibo switching office, is ex- Duncan Lorimer (all of NAIC), surveyed pected to multiply dedicated data com- the secondary subreflector in January. munication bandwidth to the AO by a Lynn Baker (NAIC, Ithaca) analyzed New era in communications factor of nearly 30 over the existing these measurements, and the panels were Daniel R. Altschuler 56Kbits/s link. reset in May. A new survey was then made, which showed very significant im- On August 27,1999 we signed an agree- Benefits of the increased bandwidth provement. ment with the Puerto Rico Telephone include faster Web access and file down- Company (PRTC), now owned by GTE, loads, real-time collaboration on exper- Encouraged by this preliminary re- to obtain Internet services from them. iments with on-site personnel, and the sult, Baker combined the new survey prospect of true remote observing. data (one target per panel) with the pho- What is unique is that PRTC agreed togrammetry data (four targets per pan- to provide and install the approximately After several years of work to find a viable solution to our communications needs, enduring the limitations of our current communications link, a new era opens up. I thank Edgar Castro, head of Electronics, Arun Venkataraman, head of Computing, and Rey Medina, head of Human Resources for their efforts which led to this development.

Talks by Jocelyn Bell-Burnell and Joe Taylor at the AO Visitor Center Duncan Lorimer On Thursday July 22, 1999, the Obser- vatory hosted a pair of special colloquia given by Jocelyn Bell-Burnell (Open University, U.K.) and Joe Taylor (Princ- eton) at the Visitor Center Auditorium.

Photo by Tony Acevedo Tony Photo by Much of the success in bringing pulsar astronomy into the public eye in recent Signing of the T1 agreement: (standing, from left to right) Rey Medina, José Alonso, Paul Goldsmith, Edgar years has been due to these two distin- Castro, and Manuel Hernández (PRTC); (seated, from left to right) José Martínez, Daniel Altschuler, and guished researchers and we were delight- John Slater (PRTC). ed that they agreed to give us two

October 1999, Number 28 20 NAIC/AO Newsletter LAN upgrade Arun Venkataraman Driven by the twin demands of increasing dataset sizes and faster, hungrier processors, a revamp of the AO Local Area Network (LAN) is under way. Coax-based, shared 10Mbit ethernet is yielding to fiber-based, switched full-duplex 100Mbit ethernet to the desktop with 1000Mbit (gigabit) backbone connections to the central switching hub. The fiber infrastructure can support future upgrades to gigabit ethernet and beyond.

New Server A Sun Microsystems Enterprise E250 with 2 x 400-MHz UltraSPARC II CPUs, 2GBytes system memory, a 200GBytes Ultra2 SCSI RAID disk array and a gigabit ethernet connection to the central switch will be the main server for recent- ly-acquired telescope data, and a high-performance compute engine for memory-intensive processing.

excellent presentations at relatively short ence of Observatory staff, our summer described in some detail the construction notice. For Jocelyn, who along with students, as well as visitors from the of the array which was made carried out Anthony Hewish just over 30 years ago University of Puerto Rico. in shifts by large fractions of the obser- was responsible for the discovery of the vatory staff, involving a lot of real hands Jocelyn’s talk recalled the remarkable first pulsar, this was her first of what we on experience in stringing out wires, chain of events that led to the serendipi- hope will be many visits to the Observa- wielding sledge hammers, etc. by her- tous discovery of the first radio pulsars tory. For Joe, this was the latest in a long self and many other graduate students of during her Ph.D. project to study the ef- series of visits as part of his on-going the day! fects of interplanetary scintillation on studies of the binary pulsar B1913+16. quasars, which began in 1967 at the Once the experiment was up and run- Jocelyn is presently based at Joe’s group Mullard Radio Astronomy Observatory ning, it was Jocelyn’s task to wade in Princeton as part of a two-year sab- in Cambridge (UK) under the supervi- through the many reels of pen-chart out- batical leave from her position as Chair sion of Anthony Hewish. The experiment put produced by the survey each day. In of the Physics Department at the Open used a dipole array operating at 81.5 addition to identifying the characteristic University in the UK. The pair of collo- MHz to cover just over 40% of the en- signals from quasars as they drifted quia were well received by a large audi- tire celestial sphere once per week. She through the telescope’s beam, she also noticed a “piece of scruff” on the output which systematically recurred at the same sidereal time as the months went by. She recalled the sequence of events that took place in order for her to con- vince Hewish and herself that the signal was of celestial origin, rather than mere terrestrial interference and showed some of the first “high-speed pen chart record- ings” which revealed regular pulsations in the data with a period of 1.337 s — the pulsar now known to astronomers as PSR B1919+21. At this point, having identified just one pulsar in the survey, Jocelyn recalled the many interesting theories as to the origins of the celestial signal, one of which was that the pulsations were be- Photo by Daniel Altschuler Photo by Daniel ing produced by an extra-terrestrial civ- ilization living on a planet in orbit around Observatory electronics and maintenance personnel installing fiber optic cable for T1 internet and telephone a sun-like star! Indeed, for a time, the service.

October 1999, Number 28 21 NAIC/AO Newsletter house beam produced early 1970s — a multi-channel filterbank by a rapidly rotating connected to a computer with a mere 32 neutron star and the ob- kilobytes of available memory which served phenomena be- was programmed in assembly language, came more compelling, together with a teletype readout and a it was becoming clear magnetic tape drive! The now legend- that the new discoveries ary pulsar search using this equipment represented just the tip began at Arecibo over 25 years ago with of the iceberg of a very Russell Hulse (now at Princeton), Joe’s much larger population graduate student, being responsible for of neutron stars in our the data taking and reduction as part of Galaxy. Finding more of his Ph.D. project. The search was indeed these objects in signifi- successful, discovering a total over 40 cant numbers would cer- new pulsars at the rate of about 2 per tainly open new and week. As Joe remarked, the automated exciting research oppor- data processing scheme they employed tunities. Since neutron even rang a bell to alert the operator that stars are expected to be a promising pulsar candidate had been lying close to the Galac- found — although this feature was sub- tic plane, where their sequently disabled following a number Joe Taylor and Jocelyn Bell-Burnell (photo by José Alonso) progenitors — the mas- of false alarms! sive stars — populate, a During the course of the survey, first pulsar was coined LGM1 — Little survey along the plane using a large tele- Hulse carried out observations in search Green Man 1. Searches for the Doppler scope should be extremely productive in mode to confirm the existence of the new shifts in the pulse period which would finding new pulsars. As Joe pointed out, be inherent in such a scenario revealed a pulsar search involves only those produced by the Earth’s mo- the exploration of a pa- tion around the Sun. This strongly sug- rameter space with typ- gested that the pulsations originated from ically over 1013 a compact star, a suspicion that was soon unknowns! Thus, the dramatically confirmed by Jocelyn’s development an effi- subsequent discovery of three further cient algorithm to dig sources from a search of many miles of out faint signals buried archival pen-chart recordings that had in the receiver noise in now been accumulated in the survey. As order to carry out sen- Jocelyn remarked: “with more than one sitive searches became source, it was highly unlikely that many his primary goal over independent civilizations were trying to the next few years. make contact with us at the same time!” Part of Joe’s de- Jocelyn’s talk closed with a summa- scription of the pulsar ry of some of the many contributions that search problem re- pulsar studies have made to Physics and called the computing Astronomy in the intervening years. One facilities available to of the most significant of these, the dis- astronomers of the day, covery and follow-up observations of the a time when large-scale binary pulsar PSR B1913+16 was de- computing power was scribed by Joe Taylor in his talk. only just becoming available. It is interest- Joe began by recalling how he got ing to compare one of interested in the pulsar discoveries short- the present “pulsar ma- ly after their announcement in 1968. As chines” here at the Ob- he remarked “the first challenge for us Fig. 21: Plot showing the cumulative effect of the orbital decay of PSR servatory with the B1913+16. The points are measurements based on timing of the pulsar was to go out and detect the things!”. instrument that Joe was over 20 years, and the line is the General Relativistic prediction. (Courtesy However, as the link between a light- building back in the Joe Taylor)

October 1999, Number 28 22 NAIC/AO Newsletter pulsars. These observations provided an As Joe mentioned in his talk, theo- neutron star-black hole binary system. independent measurement of the period, retical colleagues were quick to point out All in all, both talks were excellent which could be compared to that based to them that a pair of neutron stars in a summaries of the past and present state on the discovery observation. With the mutual orbit would be expected to show of pulsar astronomy and were well re- exception of one of the new pulsars, the up a number of effects predicted by ceived by the audience. We look forward 59 ms pulsar B1913+16, these measure- strong-field gravity. One famous predic- to further visits by Joe and Jocelyn in ments all yielded consistent results, once tion by Einstein’s general theory of rel- the not-to-distant future. the Earth’s motion was taken into ac- ativity is that the orbit should actually count. For B1913+16, Hulse observed a decay due to the emission of gravitation- systematic Doppler shift in the apparent al radiation. The fact that one of these period which implied that the pulsar had neutron stars is observable as a pulsar a radial component of velocity of up to — a highly stable clock — means that, The Angel Ramos Foundation Visitor Center in 1999 0.1% the speed of light — over 10 times for the first time, astronomers were in that produced by the Earth’s motion the position of making high-precision Jose L. Alonso and Daniel R. Altschuler around the Sun. After a few days frantic measurements of the orbital parameters The Angel Ramos Foundation Visitor observing, and visits to the library to read of a highly relativistic system. Center was inaugurated in early 1997. up on orbital mechanics, Hulse had cor- The systematic monitoring of the bi- Since its opening, more than 300,000 rectly deduced that the Doppler shifts nary pulsar by Taylor and collaborators visitors have enjoyed the experience of were being caused by the motion of the (notably Joel Weisberg, of Carleton Col- its educational exhibit program. This fig- new pulsar in a highly eccentric 7.75 lege) began shortly after these predic- ure represents an annual average of more hour orbit. Joe read extracts from tions were made. As well as a dramatic than 100,000 visitors, with children Hulse’s handwritten letter detailing the confirmation of the General Relativistic (mostly in the form of school groups and observations and recalled the excitement predictions of orbital decay (now in summer camps) accounting for 20% of of their new discovery. In these days of agreement at the 0.1% level — see Fig- the visitor flow. About 500 school groups e-mail and hi-tech communication it is ure 21) these observations have yielded are scheduled every year, representing a very sobering thought that, not so long very high-precision measurements of the all municipalities of the island. As the ago, astronomers communicated their individual masses of the two neutron only facility of its kind in Puerto Rico, it thoughts to each other via letters written stars. Hulse and Taylor were awarded the offers a unique opportunity to educate on real paper! Nobel prize in Physics in 1993 in recog- the public about the scientific endeavor. It soon became clear that the orbital nition of their discovery of this most re- Other education and outreach as- parameters of the new binary system markable binary system. pects at the Arecibo Observatory, either were most unusual. Applying Kepler’s The present campaign of measure- made possible or enhanced by the An- law to the orbital period demonstrated ments that Taylor, Bell-Burnell and gel Ramos Foundation Visitor Center, that the orbit of the pulsar was compact, Weisberg have been undertaking aim to include the Teacher in Residence pro- with a radius comparable to the physi- investigate another relativistic effect — gram, Summer Teacher Workshops, and cal size of our Sun (700,000 km). Fur- the geodetic precession of the spin axis numerous media presentations related to thermore, using formulae developed by of the neutron star about the our research areas, and often going be- optical astronomers to deduce the mass- orbital angular momentum vec- es of orbiting stars in spectroscopic bi- tor. This effect manifests itself naries, Hulse and Taylor were able to in different cuts of the neutron demonstrate that the mass of the com- star’s radio beam through our panion was about a solar mass. These line of sight as a function of two factors strongly suggested that the time causing the pulse shape to companion has to be much more com- change significantly. Indeed, pact than our Sun, and that it is probably present estimates suggest that another neutron star. Searches for radio the pulsar’s radio beam will no pulsations from the companion star longer intersect our line of sight failed to reveal it as a radio pulsar, the to this source around the year most likely explanations for this are that 2025! Perhaps by this time, its radio beam does not cross our line of pulsar astronomers will have sight, or that it has ceased pulsing alto- found even more exotic objects Graphic of visitors per year. The completion of the AOVEF, in gether. in the Galaxy to monitor, e.g. a 1997, demonstrably increased the number of visitors, and this in- crease has been sustained in subsequent years. (Courtesy José Alonso)

October 1999, Number 28 23 NAIC/AO Newsletter tory, operation, and re- exterior exhibit program (“Paseo Educa- search. Other activities in- tivo”) and a new teacher training facili- cluded a star party, ty. observation of sunspots From a teacher survey produced last and the installation and year, and given the large demand expe- operation of a weather sta- rienced during the last two years for our tion. In fact, all partici- teacher training program, a year-round pants received portable program should and could be implement- weather stations which ed. So far, over 200 teachers from are being installed in their throughout Puerto Rico have participat- schools. ed in at least one of the activities of the As part of our exhibit Center. The auditorium, which is an ex- program, we are produc- cellent resource for audio visual pro- ing “A Day in the Life of grams and lecture presentations to larger the Arecibo Observatory”, groups, lacks adequate areas to realize a 20 minute film about the workshop activities, which require a operation of the Observa- classroom like setting. For this reason, tory. The program depicts we have begun plans for construction of The Puerto Rico Secretary of Education, Victor Fajardo, during his re- some of the people and a Learning Center wing of the Visitor cent visit. events that are part of our Center. This will incorporate audio/vi- daily life. The film is cur- sual resources and appropriate furniture rently being edited by Trillium Produc- in a modern classroom setting. It will yond this to news of general scientific tions (Chicago, IL) and we expect to be used for teacher workshops, scientif- interest. have the final version by November. ic workshops and meetings, and other special groups, and student-oriented pro- Our 1999 summer teacher workshops Building upon our very successful grams. The facility will be designed by were sponsored by the Angel Ramos experience, we are planning an expan- Luis Badillo, architect of the Visitor Cen- Foundation and were held in the Visitor sion of the facilities in order to enlarge ter, in a manner consistent with the award Center from June 27 through July 9. For and improve our education and outreach winning architecture of the Visitor Cen- our first residential program, we select- effort even further. The proposed pro- ter. ed 42 science teachers from about 500 gram is divided into two components: an applicants, reflecting the great interest by the teacher community in these work- shops. The residential nature of the workshop provides a training opportu- nity for teachers throughout the Island. The Puerto Rico Secretary of Education, Victor Fajardo, visited The Center in July and was very pleased with our activities. We were also pleased by the visit last April of US Secretary of Education, Ri- chard Riley and his wife, Assistant Sec- retary Mario Moreno, and members of their staff. They spent several hours with us and expressed their admiration for our project. The main objective of this program is to provide teachers with a set of activ- ities and the necessary background to al- low them to incorporate more astronomy and atmospheric science into their cur- riculum. As part of the workshop, teach- US Secretary of Education, Richard Riley and his wife (4th and 5th from left), and members of their staff, hosted ers participated in a tour of the Arecibo by Daniel Altschuler and his wife Celia. Observatory and were exposed to its his-

October 1999, Number 28 24 NAIC/AO Newsletter ence and math sored eight undergraduates and one magnet high teacher. The NASA Capability Enhance- school in May- ment program, based at the University agüez. She of Puerto Rico’s Mayagüez campus, worked on sponsored one; the Cornell Graduate projects in con- School sponsored yet another and a third junction with the was supported by the Puerto Rico Com- Visitor Center munity Foundation under a grant to de- and its teacher velop a hypertext exhibit for the Visitor training work- Center. shops. Elba and Among the other high points of the the other summer summer program was a return visit from students conduct- the University of Puerto Rico (Río Pie- ed two very inter- dras campus) Chemistry REU program esting student with a tour of the Visitor Center and an observing atmospheric science workshop followed projects which by a pool party and barbecue. In addi- Ernesto Estremera, one of the graduating teachers of the summer workshop, re- utilized the new ceives a weather station from the hands of Dr. Francisco Carreras, executive di- tion to the regular Summer Student talks capabilities of the rector of the Angel Ramos Foundation, and José Alonso, head of the Visitor Center. by the staff, many visitors enriched the upgraded Grego- offerings. The students particularly en- rian system. joyed a visit by Yervant Terzian and Joe Another addition, the outside exhib- For the first, spectra of three lines of Veverka from the Cornell Astronomy it program, will allow visitors to experi- OH maser emission from OH/IR stars Department, and another by Joe Taylor ence the educational program as soon as (evolved stars with circumstellar shells) and Jocelyn Bell, who presented a spe- they arrive, by providing a series of ex- were taken to investigate possible vari- cial Symposium on Historic Pulsar Dis- hibits distributed along the road leading ability as compared with pre-Upgrade coveries (see article on p. 20). to the Visitor Center. This will not only observations. The second project in- Besides working hard on their make walking to the Center a more pleas- volved constructing spectra of radio con- projects, observing with the telescope ant experience, but will also incorporate tinuum sources by obtaining nearly and learning about the science that is the natural beauty of the surroundings simultaneous continuum flux densities done here, the students seemed to have a at the observatory in the exhibit program. using all of the receivers currently avail- lot of fun. The 1999 students were a The new exhibits will include a scale able on the Gregorian turret. musical group and enjoyed many eve- model of the solar system, (with sizes In addition, the students worked on nings playing guitars, singing and learn- and distances to the same scale), a solar individual research projects in radar and ing to dance salsa and merengue. The clock, and graphic panels describing our radio astronomy and atmospheric phys- students and their advisers were enter- geology, flora, and fauna. Another ex- ics with their advisers. This was the sum- tained at the annual Summer Student hibit will provide brief biographies of the mer of the observer. Many of the Party by Arecibo Observatory’s own jazz most important historical figures of our students had the opportunity for lots of band, the Hot Mofongos. Four students science. observing experience, not only with the became certified scuba divers and went As you can see, our Visitor Center is Arecibo telescope but with the Haystack deep-diving off the island of Desecheo. thriving. We are very proud of it. radio telescope and several optical tele- Besides many organized trips to local scopes as well. More detail on the Puerto Rican attractions, some students projects are presented below. also rented cars themselves and toured The 1999 Arecibo REU Summer the island. A highlight for the students Angel Alejandro, from the Universi- Student Program from the mainland was when the fami- ty of Puerto Rico, Humacao and an REU JoAnn Eder lies of several of the local students invit- student at the Observatory during the ed the group to their homes for meals Thirteen students from universities in summer of 1998, returned for 6 weeks and, in one case, a hike to a hidden wa- Puerto Rico and the mainland participat- to continue research with Sixto Gonzá- terfall with a deep pool for swimming. ed in the NAIC Summer Student Pro- lez before beginning graduate work at gram at Arecibo Observatory this year. Cornell University. Housing continues to be an increas- The program again included a local ingly perplexing problem for the stu- The NSF Research Experience for teacher, Elba Sepulveda, from the sci- dents. Adequate, convenient, affordable Undergraduates (REU) program spon-

October 1999, Number 28 25 NAIC/AO Newsletter quite gratifying, showing low surface brightness galaxies to have a deficit of neighbors in the 200 kpc range, but equal numbers of neighbors at radii greater than 400 kpc. Lilian Childress (Harvard) collabo- rated with Mike Sulzer, and by e-mail with Colin Hines, to investigate the ori- gin of the large wavenumber tail in grav- ity wave spectra by developing a new type of theory. They applied a linear- ized Lagrangian formulation to explain the gravity waves supported by the earth’s atmosphere and then transformed the simple Lagrangian input spectrum into Eulerian coordinates to see if the spectra tail would be produced. Lily developed numerical routines to support The 1999 REU Summer Students three methods of performing this trans- formation: a direct analytic approach, a one-dimensional approach based on housing was especially difficult to find 1999 SUMMER STUDENT probability theory, and a computer sim- this past summer. For students accus- PROJECTS ulation. All three approaches found the tomed to campus life, the adjustment was large wavenumber (k) tail. However, the not easy. Many staff members were very Supported by NSF REU Funds: tail varies with k-1 rather than k-3. This helpful about giving rides to the students Heidi Brandenburg (University of Min- result shows that observations, which are but late night observing and work pat- nesota) studied the correlation between made in the Eulerian frame, need to be terns made transportation critical. Solv- local galaxy density and surface bright- interpreted carefully. For example, a k-1 ing the housing/transportation problem ness in the Pegasus I & II clusters, su- tail in the Lagrangian frame is impossi- is extremely important to the success of pervised by Karen O’Neill. Heidi was ble since it implies infinite energy. future Summer Programs at the Obser- involved in all aspects of the study from vatory. Hopefully, NAIC can develop selecting the sample with a literature Nadia Fomin (Georgetown Univer- housing within walking distance of the search for cluster galaxies with no sity) searched for silicon monoxide ma- Observatory before next summer. known redshift information, to observ- sers in OH/IR stars with Murray Lewis and got lots of observing experience as Jo Ann Eder and the 1999 students ing the sample in 21 cm (over 30 hours a result. She began the summer by trav- want to especially thank all of the Ob- worth), to reducing and analyzing the eling to Haystack Observatory for a servatory staff who helped with trans- data. Although Karen was unexpected- week of observing and followed up with portation problems, particularly Eva ly away for much of the summer, Heidi many weeks of continuous remote ob- Robles, Angel Vázquez, and Murray handled the many hours of L-band ob- serving on the Haystack telescope from Lewis who transported the girls almost servation and the subsequent reductions Arecibo. By observing several samples every day, Chris Salter, Tapasi Ghosh, with only e-mail advice. with data from searches for the other and Edith Alvarez who transported the Combining the previously known masing lines found in evolved OH/IR boys, and Jonathan Friedman and Mike redshifts, estimates of the redshifts of the stars, they hoped to determine the prop- Nolan who lent their cars at various early type galaxies whose redshifts were erties which correlated with SiO maser times. Many of the students also partic- not known, and the recently taken data detection and thereby map an evolution- ularly mentioned the kindnesses of Car- which detected redshift for approximate- ary sequence of the development of the men Lydia Ruiz in the cafeteria in their ly 20 galaxies, Heidi was then able to gas and/or dust envelope of the star. evaluations. create a 3-dimensional map of the Pe- They successfully detected SiO maser gasus I and II clusters, which could be emission in 113 OH/IR stars: 59% in compared to the previously determined stars with 1612 MHz masers, 31% in central surface brightnesses of the low stars without 1612 MHz masers, and surface brightness galaxies in the clus- 63% in stars with all other masers de- ters. The end result of the project was tected. In all these classes, the detection

October 1999, Number 28 26 NAIC/AO Newsletter rate was high (84 − 97%) if the 25 mi- cility, supervised by Eva Robles, James Sheckard (Oberlin College) cron flux was above 10 Jy. The results Jonathan Friedman, and Craig Tepley. worked with Duncan Lorimer to opti- will be presented as a poster at the win- First, he created a software interface for mize the search for short-period binary ter AAS meeting in Atlanta. the CAMAC crate to control the optical pulsars. The long integration times of- instruments. Secondly, he designed an ten employed in pulsar surveys tend to Dargan Frierson (North Carolina interactive data reduction program us- reduce the sensitivity to short period bi- State University) also gained a lot of ing MatLab which streamlined and sim- nary pulsars due to Doppler smearing of experience by observing with the Areci- plified the data reduction of the the signal. Jim and Duncan developed bo telescope. Over 100 hours of L-band spectroscopy and photometry of the at- and implemented an algorithm to com- 21 cm observations were made of sam- mosphere. Finally, Ameet designed a pensate for this effect in the time and fre- ples of Seyfert 1 and Seyfert 2 active gal- Web display for the Lidar data. His real- quency domain. A ‘stack search’ of axies. The resulting HI measurements time lidar data monitor can be accessed multiple observations of the same object were used to test the unification scheme through the Observatory’s web site. increased the signal to noise ratio. The for Seyfert galaxies which states that all modified search program was applied to observed differences can be explained by Keith Nowicki (Northern Arizona previously acquired data on the globular orientation effects. If the unification the- University) participated in developmen- cluster M15 with the result that 6 of the ory is correct and the accretion disks of tal projects for the potassium resonance 8 known pulsars were found, 3 more that S1’s are face-on and those of S2’s are lidar under the direction of Jonathan had been detected with the previous edge-on, and if the HI disk is aligned Friedman. He installed and operated a search routine applied to the same data. with the accretion disk, then S1 HI spec- spectral analysis apparatus to monitor Jim also assisted Duncan in an arduous tra should have narrower velocity widths the narrow-band performance of the pulsar timing run and became familiar but the total HI mass and surface densi- pulsed alexandrite laser. This consisted with the pulsar machines currently avail- ty should be comparable. The results of a high-resolution Fabry-Perot etalon able at Arecibo. He will continue the will be presented as a poster at the win- and CCD camera with associated optics. project as a senior project and will ter AAS meeting in Atlanta. This is an absolutely necessary system present results at the winter AAS meet- for monitoring and tweaking up the per- Heidi Junkersfeld (University of ing in Atlanta. formance of the alexandrite laser. He Montana) began her project in the spring also installed the fiber optic coupling of Alicia Soderberg (Bates College) with an observing run at the Mount La- the seed laser to the alexandrite laser searched for evidence of the existence guna Observatory in California. With with the acousto-optic frequency mod- of water on central belt asteroids with Jo Ann Eder, she obtained B and V CCD ulation framework in place. This will Ellen Howell. During 8 nights at the images of a sample of gas-rich dwarf allow us to install the frequency modu- McDonald 2.1 m telescope they obtained galaxies whose HI had been detected lator with a minimum of effort needed reflectance spectra to search for the 0.7 with Arecibo observations. The sample to maintain the injection seeding of the µm absorption band. Spectra were ac- consisted of galaxies with the double- alexandrite laser. Unfortunately his ob- quired from 8 asteroids at various phas- horned HI spectra that indicate a rotat- servation period occurred during a rainy es of rotation. By dividing by the ing gas disk. The goal was to see if these week, but he gained valuable experience spectrum of a solar star, Alicia removed galaxies also exhibited organized regions on the lidar operation. any features that were solar in origin. of star formation. Although she did have She then searched for a 5% dip with a the opportunity to do some 21 cm ob- Elba Sepulveda (CROEM School- minimum at 0.7 µm. In some cases the servations with the Arecibo telescope as Mayagüez) worked with José Alonso to dip was prominent, in others it was not well, her primary task was to reduce all develop hands-on activities for the two there, and in some the band came and the optical images using IRAF. Her hard separate week-long teachers’ training went with rotation. Combining these work paid off when most of the B imag- workshops at the Visitor Center. She results with previous 3 µm observations, es of the galaxies clearly indicated the also attended all of the Summer Student they wished to test a correlation hypoth- structure associated with star formation Colloquia and contributed a great deal esis between the two features which regions. The results will be presented with her penetrating questions. A high would confirm that the easier-to-perform as a poster at the winter AAS meeting in point of her summer was participating 0.7 µm observations could be used to Atlanta. in the summer student observations of search for water of hydration. Further OH/IR stars. She was able to direct the Ameet Kini (University of Mary- observations in September should help telescope and to perform some real time land), a computer science major, devel- to clarify the conclusions. analysis. She plans to share the excite- oped several computer interfaces to ment of a research experience with her facilitate the observations and data re- high school astronomy and physics duction with the atmospheric optical fa- classes.

October 1999, Number 28 27 NAIC/AO Newsletter Supported by Other Funds test the classification of Class I and Class the next deadline. ASAC (the Arecibo Will Clarkson (Oxford U.) collabo- II masers and also as phase calibrators Scheduling Advisory Committee) will rated with José Alonso and Tony Aceve- for future surveys of masers associated recommend a course of action. with hot cores. The observations were do to develop a HyperExhibit to be The SOS will initiate an observing used to produce images with AIPS. One displayed as an exhibit in the Visitor run, monitor data quality, communicate methanol maser was found associated Center. Will used the program Dream- with PI as necessary, and seek advice ® with W3(H O) and it can be used as a weaver to design his component, 2 from scientific staff. At the end of a run phase calibrator for future observations. “Arecibo’s Universe,” the exhibit that the SOS will send the data to the observ- Carlos will continue work on the asso- focuses on the Observatory itself and the ers. work done here. The aim of “Arecibo’s ciated Q-Band VLA observations Universe” is to take the visitor into more throughout the year, as a senior project. With this new option we will be able depth than is possible with the standard He hopes to have the results ready to to schedule the telescope in a more effi- exhibits, and answer questions from the present at the summer AAS meeting. cient way, making the best use of small inquiring visitor. Will designed the fla- blocks of unused time, and also be able vor of the exhibit, mapped out its con- to alleviate the problem of the availabil- REU 2000 tent topics, and implemented the design ity of visiting scientists. The availability to the point at which the software is ready Applications for the year 2000 REU pro- of service observing will be limited by to receive the content. He has also writ- gram at the Arecibo Observatory are Donna’s commitments. We welcome ten a detailed manual for the exhibit so available from Jill Morrison, NAIC, 504 Donna to her new responsibilities. that, in the future, it can be added to and Space Sciences, Cornell University, Ith- modified easily. Will also became in- aca, N.Y. 14853. Her e-mail address is volved in the design of the interface for [email protected]. the entire HyperExhibit, of which Antonio Crespo - Employee of the Year for 1998 “Arecibo’s Universe” is a part. We look forward to the implementation of this Daniel R. Altschuler Service Observing Specialist (SOS) exhibit at the Visitor Center and its dis- Daniel R. Altschuler Last year we established the “Employee tribution to local schools. of the Year” award to recognize those Miguel Ruiz (University of Puerto Donna Kubik, an engineer previously who have distinguished themselves by Rico - Mayagüez), an engineering stu- working in the Electronics department, their great dedication going beyond the dent, gained a lot of practical experience was recently chosen to occupy the new call of duty. on a number of projects, supervised by position of Service Observing Special- ist (SOS). Department heads and members of Jonathan Friedman and Edgar Castro. the scientific staff are excluded from this He worked with the atmospheric optical In this capacity Donna will support award. A committee of five employees group to redesign the gate delay circuit- a variety of observing projects which do elected by their colleagues, receives ry for the Lidar system. The gate delay not require the presence of the observ- nominations for candidates with the ap- tells the detector to wait for a time be- ers at the Observatory. These could fall propriate endorsements and presents fore integrating so that the initial bright into one of the following categories: three finalists to the observatory Direc- signal from the Laser will not saturate tor. The prize consists of a modest cash • Short (less than 24 hours) straight- the detector. One of Miguel’s projects award and a plaque. with the engineering department was forward service observing. The 1998 recipient of the award is very beneficial for the observatory. • Completion of observing started by Antonio “Tony” Crespo. Tony started Miguel characterized the window cov- visiting scientists when it is difficult work at the observatory 27 years ago, in ering that provides RFI protection. The for them to remain for the entire run. company that manufactures the cover- 1973, as a telescope operator. His skills ing was so pleased with his results that • Queue service observing using small and initiative soon saw him working as they donated a large amount of the ma- pieces of available time on the sched- electronics technician with responsibili- terial to the Observatory! ule. ty both for the S-band radar transmitter and the maintenance of the now defunct Carlos Vargas (U. of Puerto Rico - • VLBI, pulsar timing, and other rou- HF facility. Mayagüez) worked with Peter Hofner to tine service observing. reduce the K-band observations of hot He has played an important role in Requests for this kind of support molecular cores in regions of massive the success of the new S-band radar sys- should be addressed to John Harmon, star formation. They wanted to find tem, working at any hour to assure its and will be part of our cover sheet for methanol masers that could be used to smooth operation. Tony also designed

October 1999, Number 28 28 NAIC/AO Newsletter required. Running these experiments became straight-forward thanks to the or- ganization that she put in place, includ- ing preparation of a pulsar observing manual, training the telescope operators, and setting up smooth operational pro- cedures. Kiriaki was also integral in bringing on line new pulsar back-ends. She continually championed the cause of the development of a wide-bandwidth facility pulsar processor, in order to guar- antee Arecibo a leading position in pul- sar observing for the coming years. It is poignant that this is now coming to fru- ition (see ...... ) just as she leaves us. She was also responsible for preparing and expanding the observatory pulsar docu- mentation, designing the pulsar exhibits for the Arecibo Observatory Visitor and Photo by José Alonso Educational Facility (AOVEF), and was the astronomy department representative Tony Crespo receives Employee of the Year Award from Daniel Altschuler. on the Library Committee for most of her time here. One unique development pioneered and installed our CCTV surveillance sys- us from the MPIfR in Bonn, Germany, by Kiriaki (with Bill Sisk) has been that tems and the smoke detector systems where she had earlier made the observa- it is now possible at Arecibo for up to tions for her doctoral thesis, later return- Everyone at the observatory has ex- five different pulsar observers to tap off ing there to hold a post-doctoral pressed their concurrence with the selec- of the same intermediate frequency sig- fellowship. Kiriaki came to us with a tion of Tony Crespo as employee of the nal simultaneously, each collecting data high reputation as both a talented pulsar year for 1998. Congratulations Tony! through a different back-end. This pro- observer and an extremely active team vides immense potential for collabora- member. Both these attributes were rich- tion between teams. For example, in ly confirmed during her stay with us. Comings and Goings early 1998 a consortium from Berkeley, During most of her time at Arecibo, Caltech, Jodrell Bank, MIT, NRL, Penn she single-handedly filled the role of State, and Princeton began regular Areci- Adios Kiriaki Xilouris observatory pulsar specialist, contrib- bo timing observations of millisecond Chris Salter uting immeasurably to developments for pulsars. To date (October 1999), almost twenty such timing sessions have oc- Kiriaki Xilouris left the NAIC scientific post-upgrade operations, while working curred, much of the data having been staff in August 1999 after just over four with (and for) observers, and continu- acquired personally by Kiriaki. The ex- and a half years at Arecibo. Born and ing her own impressive research pro- periment has involved 12 regular targets, raised on the island of Crete, she joined gram. Her participation in everything she became involved with was never less using 5 separate pulsar processors. than total. Following the hiatus between In respect of other observatory activ- 1993 and 1997 for the Arecibo Upgrade, ities, Kiriaki supervised a number of pulsar observing was the first astronom- REU summer students on pulsar research ical discipline to return to service. In par- projects, also lecturing to the students ticular, the on-going pulsar searches each summer that she was present. How- connected with our Upgrade recom- ever, over the past two summers she has menced in October 1996, following a made extended visits to Cornell Univer- more than one-year break, and Kiriaki sity, teaching a course there in astrono- organized the logistics for approaching my and astrophysics. In contrast, at a all-sky coverage, shipping tapes to the very practical level, she was a leading users, and generally doing everything member of the team from the Arecibo Kiriaki Xilouris (photo by Tony Acevedo)

October 1999, Number 28 29 NAIC/AO Newsletter scientific staff that (under Lynn Baker’s We are sorry to lose Kiriaki from capability, notably by getting the micro- supervision) assembled the tertiary re- NAIC, and I am sure that our pulsar user wave design software “HFSS” that mod- flector for the upgraded telescope. She community will be feeling the same. We els microwave components, including also organized a pulsar workshop at wish both her and Gene all the best for antennas. This has been used recently Arecibo in October 1995 on “Pulsar Sci- their future endeavors. We trust that by Jon Hagen to develop an improved ence with the Upgraded Arecibo Tele- when her existing pulsar projects are turnstile junction and collector for 430 scope” aimed at identifying the scheduled here at Arecibo, we will see MHz. Gene moved to Arecibo “full post-upgrade needs of the pulsar com- returning to the island both to make the time” in 1998, where he continued work- munity. observations and spend time with her ing on installing and calibrating systems, many devoted friends here. The staff as well as keeping the whole suite of re- When Kiriaki arrived in 1995, despite position she leaves at Arecibo will soon ceivers there humming along. the restrictions on local operations be filled, but Kiriaki will be “a very hard caused by the Upgrade, she advanced her Gene combined real enthusiasm for act to follow” indeed. own research through continuing pulsar radio astronomy with a down-to-earth measurements with the Effelsberg tele- Adios Gene Lauria attitude about engineering and equip- scope, augmenting these with planetary- ment development. He made real con- Paul Goldsmith nebula investigations with the Mt. tributions to NAIC and the Arecibo Palomar 200-inch telescope. Post-Up- Observatory. His dedication and posi- grade, she exploited the unique proper- tive outlook will be sorely missed. ties of the Arecibo 305-m telescope for pulsar research. Among the most excit- Bienvenidos Snezana Stanimirovic ing developments in her personal re- Chris Salter search while with us were ground-breaking studies of pulsars at millimeter-wavelengths, polarization studies of pulsars, the discovery of new pulsars (including one in close proximi- Gene Lauria (photo by Tony Acevedo) ty to the magnetar, SGR 1907+14), and investigation of the heights of emission regions in both millisecond and slower I met Gene Lauria when he was work- pulsars. Kiriaki published a well-above- ing on his MS degree in Electrical Engi- average number of quality scientific pa- neering at the University of pers during her time at Arecibo, which Massachusetts, Amherst. Gene com- was remarkable given the commitment bined the remarkable enthusiasm of an she made to the smooth operations of the amateur astronomer with an interest in Snezana Stanimirovic (photo by Tony Acevedo) telescope. radio, and pursued this combination first by working on a radio interferometer In August, we welcomed Snezana Stan- Away from scientific matters, Kiria- system for observing radio emission imirovic to Arecibo Observatory. Sne- ki is among the most caring of people. from Jupiter, and then by getting in- zana hails from Krusevac, Yugoslavia, Many of us have had personal experi- volved in developing instrumentation for and obtained her bachelors degree from ence of her kindness, whether in the af- radio telescopes. He carried out research the University of Belgrade in 1995. She termath of Hurricane Georges, helping for his MS thesis studying, both theoret- now joins us as a post-doctoral research Observatory newcomers to acclimate to ically and experimentally, the operation associate following three years in Aus- the local way of life, or in emergencies of lenses as Fourier transform systems. tralia. She recently submitted her Ph.D. such as having one’s house flooded out After a short period of working on the thesis to the University of Western Syd- (a very personal memory, this one!) staff of the Five College Radio Astrono- ney on “An HI and IR Study of the Small my Observatory, Gene joined NAIC in Kiriaki has now decided to tackle a Magellanic Cloud”. This study takes an 1993, working in the Ithaca electronics new challenge in life, and recently ac- HI and IR inventory of the SMC, a gal- laboratory. At that time, there was not a cepted a half-time position in the Cen- axy which differs from our own in mor- single receiver for the Gregorian system, tral Development Laboratory of NRAO phology, dust and gas content, and Gene threw himself into an intense at Charlottesville. She is also returning metallicity, interstellar radiation field, design, construction, and testing effort, to school, taking classes in Electrical star formation rate and evolution. For the which has resulted in the suite of cooled Engineering at the University of Virgin- HI part of this, Snezana has combined receivers that we now have. In addition, ia. We wish her well in these ventures. new Parkes observations with an ATCA he worked on upgrading NAIC’s design

October 1999, Number 28 30 NAIC/AO Newsletter synthesis mosaic to obtain a set of HI Zach is here with Tera Tagliabue, images sensitive to all linear scales be- herself a graduate in Biological Scienc- tween 30 pc and 4 kpc. (A beautiful ex- es with the highest honors in all of ample of her images was recently NMIMT. Puerto Rico offers them a very featured in “Sky & Telescope”.) From different outdoor environment. Howev- these, she has drawn exciting conclu- er, they have already qualified as scuba sions concerning the statistical proper- divers and are ready to explore the Car- ties on the interstellar medium in this ibbean waters. Welcome aboard, Zach dwarf galaxy. The IR part of the project and Tera. has involved an investigation of the dust content of the SMC using multi-wave- length IRAS data. She is also currently Adios Nirza and Pedro the principal investigator of an ATCA/ Zach Barnes (photo by Tony Acevedo) Parkes HI survey of the Magellanic Bridge. made, the position being filled by Za- Snezana has taken over the vacant chariah Barnes on 1 July, 1999. Even astronomy-department seat on the Areci- though a fresh graduate in Electrical bo Library Committee. Scientifically, Engineering from the New Mexico In- she is broadening her experience by in- stitute of Mining and Technology volvement in forthcoming pulsar spec- (NMIMT), Zach joined us with consid- tral-line observations. We wish her well erable experience in RFI-related work. with these investigations. She brings with her a fresh perspective on many Zach grew up in Silver City, New aspects of observatory-related affairs, Mexico. The vast expanse of the desert Nirza Torres (photo by Tony Acevedo) including her experience with the and mesas of the Southwest gave him AIPS++ reduction package. ample opportunity to explore nature in Nirza Torres, secretary in the Electron- many mountain biking and camping ics Department, and Pedro Torres, Tele- Snezana has already settled down trips. During those formative years, his scope Operator, both recently resigned well in Arecibo. Nevertheless, moving science teacher had a major influence in from their positions. We are sad to lose into an apartment above the local doc- shaping his interests which brought him them and wish them both well in their tor’s office might be considered an un- to NMIMT. While pursuing a bachelors’ new endeavors. usual precaution! She has already set a degree in Electrical Engineering, he new record for the speed at which she worked as a Coop student with the In- passed the Puerto Rican driving test, terference Protection Group of the VLA/ (while not implying that the velocity she VLBA. The NRAO staff members were adopted on that occasion was excessive!) so impressed with his motivation, work The whole Observatory welcomes both ethic and abilities that even after the Snezana and Matthew to Arecibo, and Coop assignment was over, they rehired we trust that their stay with us will be him for a further one and a half years on happy, fulfilling, and crowned with new various RFI-related projects. The inter- experiences and exciting achievements. ference monitoring system that he built during his time there is now a valuable Zachariah I. Barnes Pedro Torres (photo by Tony Acevedo) piece of equipment and adorns the RFI Tapasi Ghosh home page for the VLA (http:// The Observatory’s long awaited appoint- www.nrao.edu/vla/html/rfi.shtml). ment of an RFI engineer has now been

A Note to Observers We would like to remind our readers that when you publish a paper using observations made with the Arecibo Tele- scope, to please provide us with a reprint of your article. You can send reprints to: Librarian, NAIC Arecibo Observa- tory, HC-3 Box 53995, Arecibo, PR 00612.

October 1999, Number 28 31 NAIC/AO Newsletter Job Announcement – Lidar Post-Doc

The National Astronomy and Ionosphere Center (NAIC) has an opening for a Postdoctoral Research Associate in the Optical Remote Sensing Group of the Space and Atmospheric Sciences Department at the Arecibo Observatory, Puerto Rico. The Observatory is an NSF-funded National Center in space and atmospheric sciences, and radio / radar astrono- my, accepting observing proposals from scientists worldwide. Observing equipment related to research activities in space and atmospheric sciences at the Observatory include an incoherent scatter radar on the 305 m antenna, two lidars, and airglow measuring equipment. It is expected that the successful candidate will be resident in Puerto Rico and will assist in developing and carrying out a research program involving stratospheric-tropospheric exchange of aerosols and water vapor using the lidar and radar facilities. The candidate will also act as a liaison scientist in his or her area of expertise to occasionally assist visiting investigators as they conduct their own studies at Arecibo. The Arecibo Observatory is located in the karst hills of the beautiful Caribbean island of Puerto Rico. A stimulating research environment is provided by approximately 25 resident staff scientists, postdoctoral fellows and graduate stu- dents, as well as over 200 visiting scientists per year. In addition, physics and engineering faculty and students of the University of Puerto Rico have a cooperative research and educational association with the Observatory. NAIC and the Arecibo Observatory are operated by Cornell University under a cooperative agreement with the National Science Foun- dation. Applicants should have a Ph.D. in engineering, atmospheric sciences, applied physics, or a related field. Experience working with tunable lasers, interferometry, and related optics is highly desired, as is a familiarity with models of atmo- spheric transmission and minor species absorption. Depending upon funding continuity, the position would be for two years, with the possibility of an extension to three. The successful candidate will be an employee of Cornell University, and hence eligible for all relevant University benefits. Salary and benefits are competitive, attractive, and include a relocation allowance. Evaluation of applications will begin 1 January 2000, although applications received later than this may be considered. Please send a complete resume of academic, professional and personal data, a description of your research interests, and names and contact information of at least three references, to: National Astronomy and Ionosphere Center; Cornell University; 504 Space Sciences Building; Ithaca, NY 14853-6801; Attn.: J. Morrison (Lidar ORSB). EOE/AAE. For further information about the position, contact Dr. Craig Tepley, [email protected]. For general information about Arecibo, see website http://www.naic.edu.

Improved Feedback on Telescope Proposals Daniel R. Altschuler To provide our users with better feedback in relation to the outcome of proposal refereeing and the prospect of being scheduled on the telescope, we have adopted the following modification to the existing scheme. Following the referee evaluations, the Arecibo Scheduling Advisory Committee (ASAC) will place each proposal into one of these three cate- gories: A. Your proposal will remain active until scheduled. You do not need to resubmit. B. Your proposal will be scheduled only if time is available within the next two four-month periods. You will have to resubmit either the original or a revised version if not so scheduled. C. Your proposal is unlikely to be scheduled. You are invited to submit a revised version. Note that, most significantly, if a proposal is placed in the first category you are guaranteed time on the telescope.

October 1999, Number 28 32 NAIC/AO Newsletter

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