Research Paper J. Astron. Space Sci. 29(2), 141-143 (2012) http://dx.doi.org/10.5140/JASS.2012.29.2.141 Stars,Technical Companions, Paper and their Interactions: A Memorial to Robert H. Koch J. Astron. Space Sci. 28(4), 345-354 (2011) Photometrichttp://dx.doi.org/10.5140/JASS.2011.28.4.345 Observations of Eccentric Accretion in Algol-type Binary Stars Implementation and Validation of Earth Acquisition Algorithm for PhillipCommunication, A. Reed† Ocean and Meteorological Satellite Department of Physical Sciences, Kutztown University of Pennsylvania, Kutztown, PA 19530, USA Sang-wook Park1, Young-ran Lee1, Byoung-Sun Lee2, Yoola Hwang2, and Un-seob Lee1† 1 SomeGround Algol-type Systems Division, interacting Satrec binary Initiative, stars Daejeon exhibit 305-811,strange photometricKorea variations that can be phase-dependent and/or 2 secular.Satellite This System paper Research discusses Team, the Electronics possibility and of Telecommunicationsexplaining these observed Research variations Institute, as Daejeonresulting 305-700, from an Korea accretion structure eclipsing one or both of the stars. Some previous studies are reviewed and suggestions for future work are made, including the prospectiveEarth acquisition of incorporating is to solve when data earthfrom thecan Keplerbe visible Observatory. from satellite after Sun acquisition during launch and early opera- tion period or on-station satellite anomaly. In this paper, the algorithm and test result of the Communication, Ocean Keandyword Meteorologicals: interacting Satellite binaries, (COMS) accretion, Earth acquisition photometry, are presented R Arae in case of on-station satellite anomaly status. The algorithms for the calculation of Earth-pointing attitude control parameters including those attitude direction vector, rotation matrix, and maneuver time and duration are based on COMS configuration (Eurostar 3000 bus). The coordinate system uses the reference initial frame. The constraint calculating available time-slot to perform the earth acquisition 1.considers INTRODUCTION eclipse, angular separation, solar local time, and infra-redabsorption earth sensor features blinding probably conditions. resulting The results from of mass Elec -transfer, tronics and Telecommunications Research Institute (ETRI) are comparedand the with photometric that of the Astrium studies software found strange to validate variations the that implementedIntermediate-period ETRI software. Algols (those with orbital periods couldn’t be explained in the light curve models. between approximately 3 and 5 days) are not close enough A more recent study by Reed et al. (2010) made use of the toKeywords: experience Earth direct acquisition, impact of attitude accretion control from parameter, one star to time-slot, the archivalcommunication, International ocean andUltraviolet meteorological Explorer satellite (IUE) satellite other, but are perhaps too close for a stable accretion disk to data and developed a model of a variable and eccentric form. As a result, we might expect to find variable, transient, accretion structure that explained the spectral line blending and1. INTRODUCTION non-circular accretion structures in these systems. sun asacquisition well as theis completed, photometric the positionvariations. of the Reed earth (2011) is also Here we review a study of the neglected southern keptobtained in the vision new ofobservations the satellite and by adjustingcombined the them three- with those interactingCommunication, Algol-type Ocean binary and R Ara, Meteorological which modeled Satellite spectral axis inattitude the available of the satellite literature with to reference construct to thethe firstrelative ephemeris blending(COMS, Chollian) and photometric was launched variations on July as 26, effects 2010 anddue isto an position of the sun and the satellite. When the initial at- accretionnow in operation structure successfully present in (Lee the system.et al. 2011). In addition COMS to titude of the satellite is stabilized, the normal attitude is RSatellite Ara, there Ground are Controlseveral Systemother similar (SGCS) systemsis developed that bycould kept by obtaining the field of view (FOV) toward the earth Electronics and Telecommunications Research Institute by means of the earth observation sensor. benefit from further observation in order to determine (ETRI), and the algorithm of parameters and events for This paper describes mainly the earth acquisition pro- if variable and eccentric accretion can explain their COMS satellite configuration is developed according cess after the sun acquisition in case that the status of photometric variations. to the document provided from Astrium to ETRI (Laine COMS changes from on-station to abnormal. Based on 2006). the orbit information for the COMS earth acquisition, the In the launch and early operation period (LEOP) or in article describes the method to search the proper time 2.the THE situation CASE where OF R the ARAE attitude of a satellite is not nor- periods considering the constraints for calculating the mal, the satellite attitude is not known and thus it should appropriate time when the earth acquisition can be per- be Afixed good to examplea specific to direction discuss inis orderR Ara, to whose acquire orbital the nor period- formed following the sun acquisition. In case of perform- ismal 4.4 attitude. days. After The itsposition discovery of the in sun1892, is Rused Ara aswas the observed ref- ing the earth acquisition for COMS at the selected one of spectroscopicallyerences to fix the satelliteby Sahade attitude (1952) in anda specific photometrically direction. by the calculated time period, the algorithm and simulation The sun acquisition refers to the process to fix the satel- result for attitude maneuver process, maneuver time and groups in New Zealand (Nield et al. 1986, Forbes et al. 1988, Fig. 1. The ephemeris curve for R Ara, spanning 116 years since its Bankslite attitude 1990, with Nield reference 1991). toSahade the solar reported position. badly Once blended the durationdiscovery. is verified. Reprinted The from actually Reed (2011). realized earth acquisi- This isis anan Open open Access Access article article distributed distributed under under the termsthe terms of the of the ReceivedReceived Nov 15, Mar 2011 2, Revised2012 Revised Nov 23, Apr 2011 13, Accepted 2012 Accepted Nov 25, 2011 May 1, 2012 Creative Commons Commons Attribution Attribution Non-Commercial Non-Commercial License License (http://cre (http://- † Corresponding†Corresponding Author Author creativecommons.org/licenses/by-nc/3.0/)ativecommons.org/licenses/by-nc/3.0/) which which permits premits unrestricted unrestricted E-mail: [email protected] non-commercial use, use, distribution, distribution, and and reproduction reproduction in any in medium,any medium, E-mail: [email protected] provided thethe originaloriginal work work is is properly properly cited. cited. Tel: +82-42-365-7919Tel: +1-610-683-4438 Fax: +82-42-365-7500 Fax: +1-610-683-1352 Copyright © The Korean Space Science Society 345 http://janss.kr pISSN: 2093-5587 eISSN: 2093-1409 Copyright © The Korean Space Science Society 141 http://janss.kr plSSN: 2093-5587 elSSN: 2093-1409 J. Astron. Space Sci. 29(2), 141-143 (2012) Fig. 2. The International Ultraviolet Explorer light curve for Ara using Fig. 3. An overhead view of the model of R Ara, illustrating the eccentric data from 1989. The solid circles are relative fluxes measured at 1,320 Å accretion structure. Reprinted from Reed et al. (2010). and the open circles are at 2,915 Å. The solid and dashed lines correspond to the model (with eccentric accretion). Reprinted from Reed et al. (2010). curve for R Ara and found significant evidence of a steady in this paper. There are other such systems, studied in the period change due to mass transfer. The ephemeris curve is past but neglected lately, that could also be candidates for shown in Fig. 1. observing similar effects of eccentric accretion – Y Psc (Porb = The IUE data taken in 1989 provide over 4.5 days of 3.7 days) and RV Oph (Porb = 3.9 days) to name a couple. The consecutive images which are ideal for creating a light latest light curve study of RV Oph, by Walter (1970), clearly curve and analyzing phase-dependent variations. The shows outside-of-eclipse dips similar to those seen in R Ara. two prominent outside-of-eclipse dips must be due to As discussed by Richards & Ratliff (1998), short-period something cool eclipsing the primary star because they both Algols tend to undergo direct mass transfer while longer- become shallower at longer wavelengths, as shown in Fig. period systems tend to build up stable accretion disks. The 2. Also shown in Fig. 2 are the models that best fit the light intermediate-period Algol systems will oscillate between curves. These models approximate the effects of an eccentric states of direct impact and indirect accretion. It is in these accretion structure eclipsing the primary star by placing intermediate-period systems that we would expect to find large cool clouds in the line of sight. The model is restricted unstable, variable, and eccentric accretion structures. to two circular clouds, but does a fair job of fitting the data at A problem with building light cures for these systems both wavelength regions. The two cool clouds represent the from the ground is that it takes several weeks to months or locations where the eccentric accretion structure is closest even years to complete them. This complicates the analysis to the primary star. Due to the