Apollo Telescope Mount Experiments Technology

1974 (11th) Vol.2 Technology Today for The Space Congress® Proceedings Tomorrow

Apr 1st, 8:00 AM

W. C. Keathley Chief, ATM Experiments Branch, Marshall Space Flight Center, Huntsville, Alabama

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Scholarly Commons Citation Keathley, W. C., "Apollo Telescope Mount Experiments Technology" (1974). The Space Congress® Proceedings. 2. https://commons.erau.edu/space-congress-proceedings/proceedings-1974-11th-v2/session-1/2

This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. APOLLO TELESCOPE MOUNT EXPERIMENTS TECHNOLOGY

W. C. Keathley, Chief ATM Experiments Branch Marshall Space Flight Center Huntsville, Alabama

ABSTRACT

The Skylab Apollo Telescope Mount (ATM) experi Earth T s atmosphere and, during the ments, consisting of final Skylab a white light coronagraph, flight, on Comet Kohoutek. four ultraviolet instruments, two X-ray telescopes and two Hydrogen-alpha telescopes, observed the To complement the data Sun daily acquired by the orbiting for nine solar rotations. The results ATM, hundreds have of scientists around the world con only begun to be evaluated, but it is already ducted simultaneous observations apparent from their re that many theories of solar physics will spective ground based observatories undergo significant revisions as results are fur ther developed. The ATM instruments were indi Now that the Skylab mission has been completed vidually larger, more complex, and provided better and a wealth of data has been returned spatial resolution than previous to Earth solar satellite and the waiting scientists, extensive instruments. An additional major data analy advantage of the sis programs have been started. The massive telescope complex was its ability to simultaneous scientific yield will take years to evaluate but ly collect multispectral data of specific solar it is already apparent, from quick-look data, that phenomena. To maximize the scientific benefits of many theories of solar energy and mass transfer the orbiting observatory, a coordinated observing must be revised. program involving worldwide ground-based observa tories was conducted. A description of the Skylab, Limited space precludes a complete discussion of the ATM and the ATM experiments will be given. The all ATM experiments. Many technical papers could daily process of flight planning and execution will be and surely will be written on each of be described. Examples the fol of scientific data and some lowing sections. The contents of this-paper, preliminary findings will be presented. therefore, will consist of a brief description of: (1) the Skylab space station, the ATM module, and the ATM scientific instruments; INTRODUCTION (2) techniques used by flight and ground teams to collect the data; (3) samples of the solar data The Skylab Apollo and, (4) some Telescope Mount (ATM) scientific preliminary scientific findings. instruments recently completed daily observations of the Sun for nine solar rotations involving a total of 2203 hours. The line of sight from orbit HARDWARE DESCRIPTION/PERFORMANCE was a minimum of 400 kilometers above the Earth. These observations have provided scientists with Skylab Description the most complete set of continuous solar data ever accumulated and have been compared to The Skylab Space Station was launched on May 14, Galileo f s first look through his telescope cen 1973, from Cape Kennedy, Florida. As shown in turies ago. Spectral coverage of the instrument Figure 1, the launch configuration consisted of complex ranged from soft X-rays to the visible the Saturn V launch vehicle, which included the wavelengths. The spatial resolution of each in S-IC first stage, the S-II second stage and inter strument was an order of magnitude better than stage structure, and the payload, which included any similar instrument flown on previous satel the space station, instrument unit and the payload lites. A major advantage of the ATM was the shroud. The orbiting configuration, shown, in availability of astronaut observers because they Figure 2 y consisted of the Command and Service could point the instruments precisely at very Module (CSM), which was used to ferry the crew; small targets, and immediately react to unpredict the Multiple Docking Adapter (MDA), which pro able transient events. These capabilities were vided docking capability for the CSM, also housed beyond the competence of unmanned satellites. the ATM control panel and provided storage space; the Airlock Module (AM) through which the crew In addition to solar observations, the design of egressed for extra-vehicular activities; the the ATM instruments offered unique capability for Orbiting Workshop (OWS), which provided space collecting high quality for data on the Mercurian storage, experiment activities and crew quarters; atmosphere, Earth-Moon Lagrangian points, the and the ATM' module, which included the solar , .

1-1 instruments and their supporting equipment. were confined to the coarse pointing and control system (CMC failure) and the aperture doors. The The original mission plan called for a Saturn I-B CMC failure affected the maneuver times during launch of the first flight crew in the Apollo CSM excursions out of solar inertial mode and there on May 15, 1973, the day following orbital in fore indirectly affected ATM experiment operation. sertion of the space station. This plan was al Several intermittent stalls and subsequent com tered to provide sufficient time to prepare equip plete failure of the aperture doors occurred dur ment and train astronauts for in-orbit repair of ing flight. In all cases the problems were re the space station. The repair became necessary solved by utilizing a second drive motor and because one of the solar arrays and the meteoroid manually opening the door during a subsequent EVA. shield ripped away from the OWS during the May 14 launch. The repairs included the deployment of a curtain to thermally protect the portion of the ATM Experiment Instruments space station exposed by the loss of the meteoroid shield, and the manual deployment of the remaining The ATM experiment instruments consisted of the OWS solar array, which had jammed in a closed following : position. The flight crew was launched on May 29, and, almost immediately, deployed the curtain and 1. White Light Coronagraph (S052); built by Ball freed the jammed solar array, thereby literally Brothers Research Corporation of Boulder, Colo saving an otherwise-crippled space station. This rado , under contract to the High Altitude Observa was the first proof of the astronauts 1 worth to tory (HAO), also of Boulder. Dr. R. MacOueen of the Skylab program. There were many more to come. HAO is the principal investigator. Figure 3 shows the station after the repairs were made. 2. X-Ray Spectrographic Telescope (S054) ; built by American Science and Engineering Corporation (AS&E) of Cambridge, Massachusetts. Dr. G. S. ATM Module Description Vaiana of AS&E is the principal investigator.

The ATM was originally designed as a self-suffi 3. UV Scanning Polychromator Spectroheliometer cient, free-flying module and therefore contained (S055); built by Ball Brothers Research Corpora all the subsystems necessary to support the solar tion under contract to Harvard College Observa instruments contained on its optical platform. tory, Cambridge, Massachusetts. Dr. E. Reeves of During the evolution of the Skylab program, a the Observatory is the principal investigator. decision was made to hardmount the ATM to the MDA and use the ATM coarse pointing and control system 4. XUV Spectrograph/Spectroheliograph (S082) ; to maneuver and stabilize the entire Skylab and to built by Ball Brothers Research Corporation under share its large supply of electrical power with contract to the Naval Research Laboratory (NRL) , other Skylab modules. Washington, D. C. Dr. R. Tousey of NRL is the principal investigator. Figure 4 shows views of the ATM looking from the Sun end, from the side and from the MDA end. The 5. X-Ray Telescope (S056) ; built by Marshall Sun-end view shows the doors which protected the Space Flight Center (MSFC), Huntsville, Alabama. solar instrument apertures, sections of the four Mr. J. Milligan of MSFC is the principal investi solar arrays that provided electrical power, two gator. VHF telemetry antennae, two command receivers, a solar shield which thermally protected rack com 6. Two H-Alpha Telescopes; these telescopes were ponents and the Sun-end work station. The latter the primary means for boiresight pointing for the provided hand and foot restraints for the crew so ATM experiment instruments. The H-Alpha No. 1 that the astronauts could hold fast while removing instrument was actually a part of the S055 Ex and installing two ATM photographic cameras. The periment. The instruments were built by Perkin- side view shows the rack structure which supported Elmer of Norwalk, Connecticut. the pointing and control system, the solar arrays, the electrical power storage and distribution sys All ATM experiments were managed and integrated tem, the instrumentation and communication system, into the Skylab Program by the National Aeronau the center work station that provided access to tics and Space Administration's Marshall Space four photographic cameras, and the thermally con Flight Center at Huntsville, Alabama. trolled canister which housed the solar instru ments. The canister was mounted to the rack The optical layout of the S052 coronagraph is through a flexible gimbal capable of nearly 360 shown in Figure 7. Light enters the aperture and degrees rotation and plus-or-minus two degrees passes over a series of three external occulting pitch and yaw movement. The gimbal mount was disks which block out the very bright light from necessary to reduce the effect of crew motion in the solar disk and most of the associated dif side the space station on the stability of the fracted light, The effective radius of each disk optical platform inside the canister. The is approximately one and one-half times the radius arrangement of the solar instruments on the op of the Sun. The remaining coronal image is then tical platform (spar) is shown in Figure 5. As transmitted through the primary objective lens at stated before, the crew control panel for the ATM the entrance to the optics housing and then over was located in the MDA and is shown in Figure 6. an additional occulting disk which is movable in The major module problems experienced in flight pitch and yaw. Using fine sun sensors, the

1-2 internal occulting disk is automatically moved to the 2 - 60 A spectral range into approximately eliminate the final traces of unwanted scattered five spectral bands. The image is then trans light. The image is then transmitted through and ported to the photographic camera for recording. past a field lens, the Lyot spot, and a secondary In addition, a visible light path is allowed objective lens to the first fixed folding mirror, through the telescope and is recorded on the film then travels along the rear wall of the optics for calibration purposes. housing to a second fixed folding mirror. From there the image passes through a polaroid wheel to In addition to the telescope, a scintillation de the replaceable film camera. The polaroid wheel tector is coupled to a photomultiplier which pro has one clear opening and three other openings duces X-ray flux readings. These readings were filled with polaroids (60-degree E vectors). The both transmitted to the ground as scientific data polaroid position sequence is controlled by the and displayed to the crew. The output of the camera programmer and varies with the particular photomultiplier is also used to drive a flare operating mode selected by the ground or flight alarm system which provides an audible alarm when the X-ray flux reaches a threshold setting es tablished by the crew. In-flight experience re A movable mirror is located between the two fixed vealed that the photomultiplier was insufficiently folding mirrors to direct the beam to another shielded from background radiation, and conse fixed folding mirror and on to a low light level quently, the minimum threshold setting was neces television camera located on the top of the optics sarily higher than previously planned. In-flight housing. The TV image was primarily provided as problems with the filter wheel assembly will be an aid to the astronauts in pointing the instru discussed later. ments and routine coronal observations. This fea ture was essential to the accurate and rapid col The layout of the S055 instrument is shown in lection of data during fast-moving coronal trans Figure 9. Solar rays pass through the entrance ient events. The image was also transmitted to aperture to an off-axis parabolic primary mir the ground each morning for use by the ATM plan ror. From there, the rays pass through the ning group. spectrometer entrance slit which is five arc- seconds by five arc-seconds, and then on to a A design feature that also proved valuable was the grating which disperses the spectra to seven automatic logic which automatically closed the ATM photomultipliers and a zero order detector lo S052 aperture door if the angle between the opti cated on the Rowland circle focal plane. The cal axis of the coronagraph and the Sun line ex primary mirror is capable of moving in both pitch ceeded five arc-minutes. This precaution was and yaw and creates a 60-line by 60-step raster necessary since estimates showed the resulting pattern. The width of the raster is five arc- scattered light would cause permanent damage to minutes by five arc-minutes in the full raster the polaroids and the film camera shutter. The mode. The grating is capable of moving through sensor for this feedback logic was located at the an arc of six degrees to provide complete scan primary objective lens. A finer control was also ning of the entire 300 to 1300 fi spectral range. incorporated to prevent camera operation if the The possible operating modes are: above angle exceeded 20 arc-seconds, since scat tered light in that condition would mask out the 1. Mirror raster mode, during which the grating very faint coronal features which were the prime is fixed at a given position and the mirror is experiment targets. The sensor for this logic was fully rastered providing a five arc-minute by located at the internal occulting disk. five arc-minute simultaneous recording of the emissions of seven distinct wavelengths. The The S054 X-ray spectrographic telescope is depict selection of the seven lines is determined by ed in Figure 8. Light from the Sun first strikes the grating position. a thin aluminum prefilter covering the aperture of the instrument. Light then proceeds into a set of 2. Mirror line scan, during which the grating is confocal and concentric grazing-incidence mirrors. again fixed and a single selected raster line is Inside the main mirror is a small grazing-inci continuously swept to record a five arc-second dence X-ray mirror located on the optical axis by five arc-minute simultaneous recording of the that provides an image to the image dissector unit emissions of seven distinct wavelengths. (IDT). The IDT converts the image to white light and displays the results on a cathode ray tube 3. Grating scan, during which the mirror is located on the ATM C&D panel. The images from fixed at a selected position within the raster the main mirrors proceed either through or past pattern and the grating is moved to provide an the X-ray diffraction grating which has a capa emission spectra for the complete 1000 X spectral bility for mechanically moving in and out of the range. image path. This feature provides a capability of converting the telescope from an imaging device The zero-order detector was used in flight to to a spectrographic device. The primary mode used determine the coalignment of the S055 slit with in flight was with grating "out". The grating "in" the S082B slit and the mechanical reticle in the position was used primarily for recording flare H-alpha telescopes. data. From the grating, the image proceeds through one of six apertures in the filter wheel In-flight operation of this instrument was assembly. One aperture is clear and the other trouble free except for repeated cutoffs of five are filled with various filters which divide detector #5. A very sensitive current-sensing

1-3 override circuit was provided in the detector con meter. The resulting spectra is trol logic to then recorded on prevent the runaway of the high vol a film strip located at the Rowland circle focal tage power supply during high flux events that plane. A three arc-minute image of the forward could damage adjacent hardware. The threshold face of the entrance slit plate is picked off level of the override by circuit for detector #5 ap a pointing reference image dissector tube. This parently had been set at a marginal level and re image, which shows the slit superimposed peatedly on a tripped. The override circuits for the three arc-minute white light image of the other detectors Sun, worked satisfactorily but did on was displayed to the astronaut on the TV monitors occasion trip the respective detectors during high located on the ATM C&D panel. In addition, an flux events. output of the image disk tube is processed through a closed loop feedback system which rotates the The S056 optical arrangement as shown in Figure 10 primary mirror so that the slit position is similar can be to the S054 instrument in that it uses maintained on the limb of the Sun or a pre parabolic/hyperbolic grazing-incidence optics and programmed offset from the limb of the Sun. a filter This wheel to produce whole disk images of the image compensation system has the capability of Sun in the required X-ray spectral range. The maintaining a pre-determined slit position major with differences between the two X-ray instru respect to the limb of the Sun within 1 arc-second. ments are (1) the S056 instrument is an imaging device only and has no spectrographic ability, (2) A manual override of the feedback system was the collecting pro area of the S056 is less than the vided to the crew for crew pointing and was uti S054 instrument since, in the latter case, nesting lized during the last several days confocal of the SL-4 mirrors are used instead of one main mir flight when the output from the image dissector ror as in the S056 case, (3) the S054 instrument tube degraded to such an extent that the uses feed Kannigen-coated mirrors, as compared to the back system became unstable. The TV output S056 uncoated from quartz mirrors, and (4) the filters the pointing reference systems was used for in for the S056 instrument were selected to concen flight coalignment of this slit with the S055 trate on the harder X-ray emissions. With respect slit and the mechanical reticles in the H-alpha to flux measurements, the S056 instrument uses telescopes. gas-filled proportional counters instead of photomultipliers. The proportional counters are not as Hardmounted to the S082B spectrographic sensitive instrument to background radiation in orbit and, is the XUV disk monitor, a less complex consequently, instrument provide flux resolution at low providing another optical path from an levels. adjacent aperture through a thin aluminum filter onto an off-axis parabolic mirror, through another The major thin difficulty experienced with this instru aluminum filter to the face of a low light ment level was confined to the photographic cameras vidicon with a conversion layer on its face which experienced as intermittent stoppages. In all shown in Figure 13. The resulting image shows instances the malfunction was corrected by a new an integrated whole disk image of the Sun between start command by the crew. the wavelengths 150 to 650 S. This image is dis played on the TV monitor on the ATM C&D panel and The S082A diagram in Figure 11 shows the Sun f s was used by the crew for general observations rays entering through and the instrument aperture and location of certain UV features. It was also reflecting off a concave grating ruled with 3600 transmitted to the ground each morning for use in lines per millimeter. From there, the resulting the daily NOAA solar forecast. spectral images are transmitted through a thin aluminum filter on to a film strip curved around The H-alpha //I telescope -and the H-alpha //2 the tele Rowland circle position of the focal plane. scope optical layouts are shown in Figures The concave 14 and grating is movable within a three- 15, respectively. The only difference between degree angle the to provide both long and short wave two telescopes is the inclusion of a beam splitter length capability. The thin aluminum filter is and a photographic film camera in the No. 1500 X thick. 1 tele scope. The film camera in this telescope provides an ATM pointing record. Periodically The S082B in flight, is the more complicated of the S082 in both H-alpha 1 and H-alpha 2 telescopes struments. were co- It consists of a spectrograph and an aligned with the S082B and S055 instrument ultraviolet slits. monitor. In the spectrograph the The position of the movable mechanical reticle light path enters the instrument aperture and pro system on the photographic film was thus ceeds to a movable a direct off-axis parabolic mirror from record of the S082B and the S055 slit positions which it reflects through the spectrographic on the Sun. e ce slit to a predisperser grating as shown i ire 12, The entrance slit is 2 x 60 arc- Due to the similarity of the two telescopes, i only predisperser grating has two posi- the optical path of the H-alpha No. 1 telescope l the first order spectra and the will be discussed here. c second order spectra. The pre- d ' . wir grating is ruled in several bands of 150 Light from the Sun first strikes the heat a - 1 lines rejec per millimeter to offset the verti- tion window which covers the aperture of the c. . '~nin.f1?m in frrui fVic lam: entrance slit. From strument. From there, light passes to the pri t . ' . \e proceeds mary mirror, reflects to the secondary mirror in t . . • .• •. Nv ture) to the the Cassegranian system and then to the tele- t!L...-~ ,, ,..,...,.,.,.,, ,...... it ,..,-,.^^ JL.L.i.0 .,w X.LILCS per milli centric correctors located just behind the

1-4 primary mirror. The focal plane of the telescope importance was the continual excellent perform is located behind the telecentric correctors and ance by the astronauts as solar observers. This the mechanical movable reticles are located at was particularly demonstrated in the acquisition this position. The beam progresses into the of literally hundreds of recordings of transient Fabry Perot filter system that includes an 8 X solar events. Most of these events, which were blocking filter and an 0.7 X Fabry Perot filter. not predictable, could not have been collected by Both filters are thermally controlled by the same unmanned observatories. Nor could unmanned ob filter oven. From there the beam proceeds to the servatories have so precisely pointed the beam splitter and the two small resulting beams are fed, field-of-view instruments to the in one case, through additional proper point in field lenses to the structure of comparatively small targets. the photographic camera and, in the second case, through a 5X zoom lens to the vidicon television camera. Due to its wider field of view (35 arc- FLIGHT PLANNING AND EXECUTION minutes), the H-alpha 2 telescope was primarily used by the crew for total disk observations. The An important concept for future missions H-alpha 1 telescope was was primarily used for precise developed and proven by the ATM experimenters pointing due to its smaller available field of with respect to solar observing programs. view (4 arc-minutes) In the and higher spatial resolution beginning, the five ATM principal investigators on the TV monitor. proposed individual scientific programs, each with several distinct objectives. Efforts to Considering the complexity of the instruments, the integrate these individual observing programs in overall performance was excellent. The major pro to practical flight procedures revealed a large blems encountered were confined to the photo number of over-lapping objectives. The total graphic subassemblies. Out of the 30 replaceable required crew time, even after considering over cameras and magazines flown, two jammed and six lapping objectives, exceeded the amount of crew displayed intermittent film transport problems. time available and, additionally, astronaut In all cases the failed or troublesome subassembly training was already extremely complicated. A was replaced by the crew during a subsequently simplified and more efficient approach was ob scheduled EVA and relatively small amounts of ob viously required. serving time were lost. A small group of ATM science representatives and Two other problems are worth noting here since the NASA flight planners was formed to solve the resolution of these problems also demonstrated the problem. Consistent with the traditional scien benefit of having an in-flight crew. tific method, the group first defined the solar physics problems that it wished to investigate. Early in the first Skylab flight, a piece of cloth Considering the available current theories of thread found its way onto the front external mass and energy transfer for each problem, the occulting disk of the S052 coronagraph, which re group then formulated a collective plan for ac sulted in a large degree of localized scattered quiring the required data and identified each light. The resulting effect is shown in Figure instrument's possible contribution to the process. 16. During the mid-mission EVA on the first The required data-collection sequences were flight Commander Conrad reached through the in determined and subsequently adjusted where proved strument aperture and removed the contaminant with necessary during many crew practice sessions, or a brush. This feat was particularly remarkable simulations, on the ground. since the cleaning of any optical surface is always a delicate operation even in a laboratory. The end product of the ATM working group The coronagraph performance was a was completely re list of Joint Observing Programs (JOPs) and the stored. associated problem definitions. During the latter part of the final Skylab manned A list of the Skylab JOPs are given in Table 1. flight the filter wheel inside the S054 X-ray JOPs 1 through 14 were defined for the initial telescope failed to move, sticking between two SL-2 flight. JOPs 15 through 17 were added for filter positions. All efforts to solve the prob the second manned flight (SL-3) as a result of lem via remote commands from ground controllers the SL-2 quick-look data analysis and crew com failed. During a subsequent EVA, Commander Carr ments. JOPs 18 through 27 were subsequently removed the S054 photographic magazine and used added for the final manned flight (SL-4) to add a screwdriver to move the wheel to a preselected certain observations identified as filter position, restoring the instrument to during the two previous flights, .MM-.- r< r JOPs nominal operation for that filter position. This also added a program to observe Comet Kohoutek. accomplishment was also remarkable in that Com mander Carr, limited in mobility by his "hard" Using the available instrument operating modes, EVA suit, was able to insert the screwdriver the group then defined the data collect:?or? pro through a small camera aperture, past the shutter cess in terms of building blocks, blades and pry the wheel to the desired position. precise time during each orbit whe. ^^r mode for an instrument was to be i It should be noted that the flight crew's in most cases TTT-. - . -; ".-- •••-.•'. ",-n.-" *-.--. ./as re volvement was not limited to removing and instal quired for fe-- -s, a ling cameras and repairing failed components. given buildj ' than Those contributions were important, but of no less one JOP. Tht^- , f ^,..i>,,-,,^ ; - , ..;r.s, LH^ r^.t.^ij-a

1-5 pointing instructions, and appropriate photographs inputs to the next day's Detail Flight Plan at for visual aids, were then placed on a single sheet noon, each day. Using the time blocks allocated of paper, called a JOP Summary Sheet. These sheets to the ATM on the DAY N + 1 SFP, the morning tele were then used for crew training and subsequently vision transmission to ground of the video dis became part of the on-board flight data file. A plays, the NOAA solar forecasts and the crew com sample of a JOP summary Sheet is shown in Figure ments from the previous day, the ATM 17. The pointing instructions planners de are listed on the termined and scheduled the specific JOPs which left top side of the sheet, the applicable build they wished executed on the following day. These ing blocks on the right and the visual aid in the planning inputs were then transferred to the De lower left hand side of the paper. A similar set tail Flight Planning (DFP) personnel for negotia of building blocks were defined for use in the tion on the subsequent shift. The DFP represen unattended and unmanned modes. tatives then reviewed and processed the require ments in flight planning terminology to the In retrospect, it is impossible to visualize fly Flight Activities Officer who subsequently trans ing the ATM mission without employing a JOP pro mitted them to the spacecraft during the follow cedure. Intelligent flight planning, which is ing Summary Shift. The Detail Shift also pre discussed in later paragraphs, would have been pared the unattended command plan for those ob extremely difficult and the excellent crew per servations that were to be executed via remote formance that was demonstrated on all three mis commands during the time when the crew was not sions would have been seriously hampered. available. Flight planning and subsequent execution by the The various Mission Control Center locations that flight and ground crews involved a daily process were involved in the daily ATM flight planning that demanded timely inputs, efficient operation are shown in Figure 19. The Mission Operations by all parties, and crisp communication loops. Control Room (MOCR) was staffed by the various The Joint Observing Program discussed above pro Skylab functional groups and was under vided a common language the super and therefore was the key vision of the Flight Director. The ATM Activities to achieving the ATM requirements. Officer was the primary ATM voice to the Flight Director on all ATM matters. He was supported In spite of the simplifications by afforded by the the ATM Science Room and a Staff Support Room. JOPs, the daily flight planning process was still The Science Room was staffed by personnel from complicated. The procedures were formulated and each PI organization, NOAA and a Flight Control iterated several times during pre-flight simula Division representative. All science questions tions and some modifications were made even during from either the MOCR or the crew were directed the initial manned flight. The process described to this group. The Staff Support Room was res in the following paragraphs represents the final ponsible for all real-time engineering inputs, established procedure. short-term trend analyses, mission status and all ATM remote commands to the spacecraft. Figure 18 represents the major activities for a typical day, Day N. The day was divided into Representatives in the Planning Room and an off three shifts; namely, the Summary Flight Planning line Data room where quick-look data analyses Shift from midnight to 0800 hrs Central time, were conducted, and representatives at the the Execute Shift from 0800 hrs to 1600 hrs and various hardware contractor plants, were in di the Detail Flight Planning Shift from 1600 hrs to rect support of the Science Room activities. midnight. As the name implies, the Summary Shift personnel produced the Summary Flight Plan (SFP) The Flight Operations Management Room (FOMR) for the following Day , (N + 1). The SFP contained staffed by technical and management personnel assigned allocations of each crewman T s time, time from each program element, was in direct support of each day-night cycle, vents schedules, momentum of the Flight Director. This group acted es dump inhibits of control moment gyros, video tape sentially as a real-time change board for rulings recorder schedules, television transmissions to on mission requirements. The Skylab Mission the ground, ground station coverage, star tracker Scientist occupied a seat in the FOMR. update schedules ATM non and general comments to the crew. real-time engineering support from The negotiation the Huntsville of assignments of blocks of time Operations Support Center was available to each through Skylab group of experiments occurred on the ATM desk in the FOMR. this shift. To assist them in these negotiations, the ATM representatives used the accomplishments from the previous day's flight, the long range SCIENTIFIC RESULTS planning inputs from the ATM planning group, the long-range solar forecasts from the National All ATM instruments met, and in many instances Oceanic and Atmospheric Agency (NOAA), and the exceeded, the optical design specifications given results of prior negotiations from the bi-weekly in Table 2. Relatively few functional problems Skylab Science Planning meetings chaired by the were encountered. Whenever a problem did occur, Skylab Mission Scientist. The Detail Flight Plans the crew was able to solve it by replacing or re (DFP) for DAY N were transmitted via a teleprinter pairing the failed system on the next EVA or by to the crew during this shift. utilizing appropriate backup operational modes. Concurrent with the execution of the DAY N flight In terms of quantity of data accumulated, Table plan, the ATM Planning Group began preparing their 3 shows the premission planned quantity as com-

1-6 pared to the actual quantity acquired. Table 4 Mechanisms associated with solar flares erupting gives the total hours of observing time accumula from active regions such as the regions shown in ted in the manned, unattended and unmanned modes. Figure 22 are being, reinvestigated. The S056 Manned time represents the observation time ac X-ray instrument recorded literally hundreds cumulated by the flight of crews. Unattended time X-ray brightenings during the course refers to the of the three observation time accumulated via RF Skylab flights. Some cases remote fit classic flare commands while the flight crews were on theory, some do not. board but participating in other Skylab experiments or asleep. Unmanned time was acquired during the The effect of chromospheric oscillations on unmanned storage periods between the three Skylab coronal heating is being questioned since no evi manned flights. It should be noted that only the dence of such an effect has been found to date in S052, S054 and S055 instruments nominally operated the ATM data. in the unattended and unmanned modes. Recent correlation with meteorological data Samples of the scientific have data collected by the indicated that passage of the solar-induced ATM instruments are shown in Figures 20 through interplanetary magnetic sector boundary 26. Some of the preliminary affects findings derived from the incidence of large storms in the northern these and other similar data are as follows. hemisphere of Earth. Since the magnetic sector boundaries generally coincide with coronal hole Numerous visual changes in coronal structure, such boundaries, the possibility of long-range Earth- as the streamers shown opposite the large tran weather predictions appears possible. sient in Figure 20, have been observed over small er increments of time than originally expected. Whether such changes are a result of dynamic re SUMMARY arrangements in the corona, or perspective effects of particular coronal geometries, will require The data collected by the various ATM instruments further detailed study. is already proving its value in verifying and re vising certain conventional theories of solar Conventional models of coronal expansion predict physics. The data will furnish a reference base that material is accelerated through the field of for future analyses and further experimental work view of the coronagraph in about two days. Pre in solar physics for years to come. This, of liminary visual examinations of the S052 photo course, was the major overall objective graphs of the fail to show any such material flow, but a project. But other project accomplishments final conclusion will cannot be reached until detailed certainly prove worthwhile precedents for digital future reduction has been accomplished. missions. Specifically, they are: Coronal "voids", or dark lanes, amidst coronal 1. Formulation and successful implementation streamers of where the electron density is substan the Joint Observing Program concept. tially reduced, have been discovered. The mechan isms which form, maintain and terminate these 2. Formulation and successful implementation of voids are unknown at this time. the coordinated observing program with worldwide ground-based observatories. The high frequency of coronal transient events such as that shown in Figure 20 was totally un 3. Outstanding functional and optical perform expected. ance of all instruments. X-ray photographs of the very hot corona such as 4. Crew performance as solar observer. shown in Figure 21 have completely destroyed earlier concepts of a "quiet, homogeneous corona". 5. Crew performance in repair of instruments. On the contrary, the corona is seen to be composed of a variety of highly complex structures which 6. High quantitative yield of scientific data. either are directly associated with underlying photospheric and chromospheric features, as in the case of active regions, or are indirectly related ACKNOWLEDGEMENTS to such features. The coronal holes, which appear in the photographs as areas of little or no X-ray It would be impossible to properly acknowledge emission, all appear to be the exceptions to this pre the people who have participated in the process liminary finding. of making the ATM the success it was. The prin cipal investigators and their contractors men New concepts of the total contribution of bright tioned in the body of the paper, the MSFC experi points are being developed. Such bright points ment engineers, the MSFC ATM project staff, the are shown in Figure 21 as small points of emis ground test teams, the flight controllers and the sions approximately 30 arc-seconds in diameter and flight crews all performed their functions in an can be clearly seen in the coronal holes and at outstanding professional manner. My association the polar regions. The short lifetime of the with them has been one of the most rewarding bright points, the random occurrence over the aspects of the project. entire disk, the intense brightness and their similarity to solar flares are all subjects of I would like to give special thanks to Jack extreme interest to the solar physicists. Dollar of Sperry Rand Corporation and Jim Cain,

1-7 Jack Braly and Jim McKechnie of Martin Marietta Manned Space Flight/Office of Space Science, Corporation who assisted in gathering the infor Washington, 1973. mation for this paper.

ILLUSTRATIONS BIBLIOGRAPHY

Davis, J. M., Giacconi, R., Krieger, A. S., Silk, Figure 1. Skylab Launch Configuration J. K., Timothy, A. S., Vaiana, G. S., and Zombeck, Figure 2. Orbiting Skylab Configuration M.: "X-ray Observations of Characteristic Struc Figure 3. Repaired Skylab tures and Time Variations from the Solar Corona: Figure 4. ATM Module Preliminary Results from Skylab." Astrophysical Figure 5. Instrument Arrangement Letters, New York, Vol 185, 1973. p L-47. Figure 6 . Astronaut Ed Gibson at ATM C&D Panel Figure 7. S052 Optical Schematic Bernazea, J. E., Huber, M. C. E., Noyes, R. W., Figure 8. 5054 Optical Arrangement Reeves, E. M., Schnahl, E. J., Soukal, P. K., Figure 9. 5055 Optical Schematic Timothy, J. G., Withbroe, G. L. : "Observations of Figure 10, 5056 Optical Schematic the Chromospheric Network: Initial Results from Figure 11, S082A Optical Schematic ATM." Astrophysical Letters, New York, Vol 187, Figure 12, S082B Optical Schematic 1974. p L-l. Figure 13, XUV Monitor Optical Schematic Figure 14, H-Alpha-1 Optical Schematic Eddy, J. A., Gosling, J. T., Hilner, E., MacQueen, Figure 15, H-Alpha-2 Optical Schematic R. M., Munroe, R. H., Newkirk, G. A., Jr., Poland, Figure 16. S052 Contamination Scattered Light A. I., Ross, C. L. : "The Outer Solar Corona as Figure 17. Jop Summary Sheet Observed from Skylab: Preliminary Results." Figure 18. Day N Planning/Execution Cycle Astrophysical Letters, New York, Vol 187, 1974. Figure 19. ATM Flight Support Locations p L-85. Figure 20. Mammoth Solar Eruption Photographed by S052 Davis, J. M., Giacconi, R., Krieger, A. S., Silk, Figure 21. S054 X-ray Photograph of the Solar J. K., Timothy, A. S., Vaiana, G. S., and Zombeck, Corona M.: "Preliminary Solar Extreme Ultraviolet Ob Figure 22. S056 Photograph of Sun in Soft X-ray servations from the ATM with the Harvard Instru Region ment." The Bulletin of the American Astronomical Figure 23. Helium Eruption Recorded by S082A Society, New York, Vol V, 1973. p 419. Figure 24. Ultraviolet Absorption in the Earth's Atmosphere Davis, J. M., Giacconi, R., Krieger, A. S., Silk, Figure 25. S055 Variable Density Plots of Large J. K., Timothy, A. S., Vaiana, G. S., and Zombeck, Solar Prominence M.: "Prominences in EUV as observed from ATM." Figure 26. H-Alpha Photograph of Solar Flare The Bulletin of The American Astronomical Society, New York, Vol V, 1973. p 432. Table 1 Joint Observing Programs Table 2 Prime Instrument Design Parameters Davis, J. M., Giacconi, R. , Krieger, A. S., Silk, Table 3 ATM Experiments Data Quantity J. K., Timothy, A. S., Vaiana, G.S., and Zombeck, Table 4 Solar Observing Time M.: "A Study of the Active Region McMath 12417 with the Harvard ATM EUV Spectrometer." The Bulletin of The American Astronomical Society, Vol V, 1973. p 432.

Davis, J. M., Giacconi, R., Krieger, A. S., Silk, J. K., Timothy, A. S., Vaiana, G. S., and Zombeck, M.: "ATM Observations of Solar Flares in Extreme Ultraviolet." The Bulletin of The American Astronomical Society, New York, Vol V, 1973. p 433.

Davis, J. M., Giacconi, R., Krieger, A. S., Silk, J. K. , Timothy, A. S., Vaiana, G. S., and Zombeck, M.: "Observations of the Coronal Hole Boundary in the Extreme Ultraviolet." The Bulletin of The American Astronomical Society, New York, Vol V, 1973. p 446.

Goleub, L., Krieger, A. S., Silk, J. K., Timothy, A. S., Vaiana, G. S.: "Solar X-ray Bright Points." Astrophysical Letters, New York. To be published 15 April 1974.

Skylab and the Sun. NASA EP 119. National Aero nautics and Space Administration, Office of

1*8

WORKSHOP

- -

ADAPTER

Configuration

CYLINDER

ASSY ASSY

SHROUD

SHROUD SHROUD

UNIT UNIT

—————— ——————

ARRAY ARRAY

Launch Launch

MODULE

SHROUD SHROUD

PAYLOAD PAYLOAD

AIRLOCK AIRLOCK

PIVOT PIVOT POINT

DEPLOYMENT DEPLOYMENT

SOLAR SOLAR ARRAYS

DEPLOYMENT DEPLOYMENT

Skylab Skylab

AIRLOCK AIRLOCK

INSTRUMENT INSTRUMENT

ATM ATM ASSY ASSY

OWS OWS

MULTIPLE MULTIPLE DOCKING

UPPER UPPER

ATM ATM

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1. 1.

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ATM ATM

APOLLO APOLLO

SOLAR SOLAR SHIELD

Configuration

lab lab

Sky Sky

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. .

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Figure Figure

ASSEMBLY

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END) END)

ADAPTER

DEPLOYMENT DEPLOYMENT

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SERVICE SERVICE

WING WING

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ARRAY ARRAY

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ATM ATM ATM ATM Figure 3. Repaired Skylab

1-11

WING WING

\ \

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H-ALPHA 1 TELESCOPE H-ALPHA 2 TELESCOPE

S055A UV SCANNING S082B XUV POLYCHROMATOR SPECTROGRAPH SPECTROHELIOMETER

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FILM FILM CAMERA CAMERA LOW LIGHT LEVEL VIDICON TV CAMERA TV CAMERA MDA END

(FLAT LAYOUT)

Figure 5. Instrument Arrangement 1-13

Panel

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ATM ATM

at at

Gibson Gibson

Ed Ed

Astronaut Astronaut

6. 6. Figure Figure

HANDLE HANDLE

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ONLY)

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Figure Figure

OCCULTING OCCULTING

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INTERNAL INTERNAL

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Figure Figure

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Figure 10. S056 Optical Schematic CONCAVE GRATING

LONG WAVELENGTH ZERO ORDER REJECTION MIRROR SHORT WAVELENGTH ZERO ORDER (A) REJECTION MIRROR IN HORIZ POSITION DATA FLASHER +Y THIN ALUMINUM FILTER FILM STRIP

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'CONCAVE GRATING ROTATED 3° LONG WAVELENGTH ZERO ORDER REJECTION MIRROR SHORT WAVELENGTH ZERO ORDER REJECTION MIRROR IN VERTICAL POSITION DATA FLASHER THIN ALUMINUM FILTER (B) FILM STRIP SPACECRAFT INSTRUMENT ENTRANCE ENTRANCE APERTURE APERTURE

EXTERNAL REJECTION MIRROR

Figure 11. S082A Optical Schematic 1-19

PREDISPERSER PREDISPERSER

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JOP JOP cn TIME: DAY N 0000 MRS- DAY N-l ACCOMPLISHMENTS————————*• DAY N-l ATM PLANNING GROUP INPUTS—* NOAA FORECASTS———————————————>• SL SCIENCE MEETING INPUTS PRODUCTION OF DAY N+1 SUMMARY UPLINK DAY N FLIGHT PLAN PADS TO CREW

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EXECUTION OF DAY N ATM PLANNING DETAIL GROUP — FLIGHT PREPARE DAYN+1 PLAN DETAIL FLIGHT PLAN INPUTS TIME: 1600 MRS-

PRODUCTION OF DETAIL FLIGHT PLAN FOR DAY N+1

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Figure 18. Day N Planning/Execution Cycle

1-26

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