Attitude Data (ATNM Type) ========================= General information about ESOC Attitude Data for Mars Express ------------------------------------------------------------- Attitude data are provided for all mission phases apart from safe modes. Except for initial launcher separation and for backup modes the attitude is contorlled in one of the following ways: - The S/C takes a fixed inertial attitude commanded by ground. - The S/C follows a time dependent attitude profile commanded by ground - The S/C x-axis is Earth Pointing, the S/C y-axis is nearly to the ecliptic. Time dependent inertial Earth and Sun direction profiles are commanded by ground. The attitude information in this file is based on command profiles. There is no distinction between cruise phase and operational orbit as for orbit ephemeris, since that is not necessary in terms of attitude. The attitude is provided in segments, each covering a specific time span. These segments have no overlap. There may be gaps between the segments and even gaps in the segments. Attitude data have been provided for the past and near future during the operational mission. Predicted vs. Reconstituted Attitude Data ----------------------------------------- Except special cases, no reconstituted data have been provided for Mars Express attitude information. Despite that originally it was stated that reconstituted attitude data would be provided for certain pointing modes as a Flight Dynamics official product, this was denied and removed from the official documents after the Near Earth Verification (NEV) Review even when these data were requested several times by the Principal Investigator (PI) teams and it was flagged as something the scientist would need. The reason to not provide reconstitution for the attitude data can be sumarized in the following points: - The attitude estimation from the S/C onboard filter could not be improved on ground with the available Attitude and Orbit Control System Telemetry. - The divergence on the pointing of the onboard estimated attitude from the Flight Dynamics provided predicted attitude in the DDS is below the specified requirements and in the order of the measurement noise. Representation of Attitude Data ------------------------------- The attitude of the S/C refers always to S/C frame (also called S/C reference frame) with respect to the reference frame J2000. The pointing of a Mars Express spacecraft is described by the rotation of the S/C reference frame with respect to the J2000 reference frame. This rotation is usually represented by a 3x3 matrix, called C-matrix which is used to perform the transformation of the three components of a vector in the J2000 frame to components expressed in the spacecraft reference frame. The attitude of a payload instrument can be derived by applying the rotation between the instrument frame and the S/C frame. So, it is possible to obtain the orientation of any instrument by matrix multiplication. The rotation matrix can be represented by a quaternion, which is a four-dimensional vector that represents a unit vector (3 components) and an angle. The vector represents the axis of rotation, and the angle the rotation magnitude. Attitude Data Access. Data Storage. ----------------------------------- Attitude data have to be stored in a binary direct access data file in a format that is tailored with respect to numerical accuracy, access performance and storage requirements. This applies to the S/C predicted attitude (and in special cases, reconstituted). Although the low level architecture of data storage is quite sophisticated the retrieval of data is made very easy by the use of a simple access software. The attitude file contains attitude information at discrete times. The corresponding epochs are not equidistant in time but are chosen by numerical integrator. Attitudes for arbitrary epochs are derived by interpolation. The whole attitude is partitioned into blocks which comprise a mission phase or a part of it. For each block and for the whole file there is additional information stored in block headers and the file header. All data are stored in logical records containing either attitude, block header or th file header information. The logical records are in turn grouped together into the physical records of the binary direct access file. The access software (archived within this data set) reads the data only from binary direct access files. To allow the transfer of data between machines which are not binary compatible, attitude data have been made available in ASCII format together with a FORTRAN utility for conversion into the required binary format on the target platform. This ASCII files have been archived in this data set as well as the FORTRAN program. To access an attitude at a certain epoch from a FORTRAN application program, a library is provided together with the attitude data. This software is described in the SOFT.CAT catalogue. ASCII Version of the attitude file ---------------------------------- Although content and structure of the ASCII file is completely transparent to the user (only the conversion with AS2BIN is required to create a valid binary attitude file), a short description follows. The ASCII file contains several blocks of data. Each block has a leading descriptive part, called meta data, consisting of a list of keyword value pairs surrounded by the identifying META_START and META_STOP keywords and the attitude data part proper. The following keywords appear in the meta data: - CREATION_DATE Date and time of file creation - OBJECT_NAME Identification of object (MARS EXPRESS) - TIME_SYSTEM always TDB, i.e. barycentric dynamical time - REF_FRAME reference frame, always 'EME 2000' = mean Earth equator of J2000 - START_TIME start of time interval covered by the following block of data - STOP_TIME end of time interval covered by the following block of data - FILE_TYPE always 'ATTITUDE FILE' - VERSION_NUMBER indicates the version of the file format - VARIABLES_NUMBER always 4 - DERIVATIVES_FLAG always 0 The proper attitude data are just lines providing at discrete time steps epoch of the state and the quaternion describing the rotation from the inertial to the S/C frame. Orbit Data (ORHM and ORMM Types) ================================ General information about ESOC Orbit data for Mars Express ---------------------------------------------------------- Orbit determination has been a batch least squares procedure taking into account range and Doppler measurements from the European Space Agency 35m antenna at Perth. During critial mission phases tracking data have been additionally provided by ESA/Kourou and NASA/DSN stations. The dynamical model of the S/C motion refers to the J2000 inertial reference frame with Barycentric Dynamical Time (TDB) as independent variable. In addition to the Newtonian attraction of the planets and the Moon, the model includes: - Relativistic corrections to the gravitational fields. - Perturbations of the Earth and Mars gravitational fields due to oblateness. - Solar radiation pressure forces. - Orbit manoeuvres. - Small forces due to gas leaks or uncoupled control jets. The centre of integration depends on the mission phase. Near Mars the orbit is integrated with respect to the planet. During cruise phase the centre is the Sun. The ephemerides of the planets and Moon are taken from the latest version DE4005 of the Jet Propulsion Laboratory (JPL) export ephemerides files. Range and Doppler measurements are corrected for several effects: - Transponder delay. - Signal delay due to the troposphere and ionosphere of the Earth. - Signal delay due to interplanetary plasma. The result of the least squares prcedure are best estimates of the state vector of the S/C and of severalmodel parameters plus statistical information. The accuracy depends on the mission phase. The number and frequency of batchs runs for the orbit determination depends on the mission phase and the availability of tracking data. For the cruise phase has been done tipically every month (at least once) while for Mars Orbit phases the process is executed once a week. Two types of orbit data have been provided for the Mars Express mission. One, named ORHM type, covered the cruise phase from launch to Mars Orbit Insertion (MOI), the second, called ORMM type, the operational orbit around Mars after orbit insertion. For all types, the reference plane is the Earth mean equator of J2000. The orbital data have been provided during cruise phase as heliocentric states, in the operational orbit as Mars centric states. Data of the first type (ORHM) is contained in a single file. With each new orbit determination and/or manoeuvre optimisation, a new version of the file has been created. Only the latest version of the file (00038) has been archived in this data set. Data of the second type (ORMM) have been distributed over several files due to the large amount of data. The name of the file contains the start time YYMMDDhhmmss of the interval which is covered by the file. As there are no gaps between files, the corresponding end tyme of a file is given by the start time of the next file. The time interval is tipically about one month. The start time in the file name has been given to an accuracy of a day (i.e. hhmmss = 000000) and is accurate to one day compared to the actual time spancovered by the data in the file. For example, the file with YYMMDDhhmmss = 040309000000 contains data starting at any time between 08/03/2004 and 10/03/2004. This has been done in order to keep some freedom in the choice on the actual separation of data in time. This separation has taken into account operational conditions like correction manoeuvres. Predicted v. Reconstituted Orbit Data ------------------------------------- The orbit prediction uses the same dynamic model and similar integration techniques as for orbit determination (described in the previous chapter -- General information about ESOC Orbit data for Mars Express). But instead of fitting the S/C orbit in the past with received tracking data the future S/C orbit is integrated using the best estimate of the last orbit determination and optimized with respect to fuel consumption and mission constrains by suitable insertion of manoeuvres. Reconstituted data have been delivered with every update of the files. Although these files, when delivered to the PI teams contained both predicted and reconstituted orbit data, the latest version (archived in this data set) of each file contains only reconstituted data. Orbit Data Access. Data Storage. -------------------------------- Orbit data have been stored in a binary directo data access file in a format that is tailored with respect to numerical accuracy, access performance, common application interface and storage requirements. This applies to the S/C recontructed and predicted orbits (not available). Although the low level architecture of data storage is quite sophisticated the retrieval of data is made very easy by use of a simple access routine. The orbit files contain orbital information at discrete times. The corresponding epochs are not equidistant in time but have been chosen by the numerical integrator. The whole orbit is partitioned into blocks which comprise a mission phase or a part of it. For each block and for the whole file there is additionalinformation stored in block headers and the file header. All data have been stored in logical records containing either orbital, block header or file header information. The logical records are in turn gruoped together into the physical records of the binary direct access file. The access software (archived within this data set) reads the data only from binary direct access files. To allow the transfer of data between machines which are not binary compatible, orbit data have been made available in ASCII format together with a FORTRAN utility for conversion into the required binary format on the target platform. This ASCII files have been archived in this data set as well as the FORTRAN program. Read access has been established by a layer of low level FORTRAN subroutines on top of which a very simple FORTRAN access subroutine resides. This subroutine is described in the software catalogue of this data set (SOFT.CAT). ASCII Version of the orbit files -------------------------------- Although content and structure of the ASCII file is completely transparent to the user (only the conversion with AS2BIN is required to create a valid binary orbit file), a short description follows. The ASCII file contains several blocks of data. Each block has a leading descriptive part, called meta data, consisting of a list of keyword value pairs surrounded by the identifying META_START and META_STOP keywords and the orbit data part proper. The following keywords appear in the meta data: - CREATION_DATE Date and time of file creation - OBJECT_NAME Identification of object (MARS EXPRESS) - TIME_SYSTEM always TDB, i.e. barycentric dynamical time - REF_FRAME reference frame, always 'EME 2000' = mean Earth equator of J2000 - CENTER_NAME Identificiation of central body, e.g. SUN, MARS. - START_TIME start of time interval covered by the following block of data - STOP_TIME end of time interval covered by the following block of data - FILE_TYPE always 'ORBIT FILE' - VERSION_NUMBER indicates the version of the file format - VARIABLES_NUMBER always 6 - DERIVATIVES_FLAG always 1 (state and state derivative provided) The proper orbit data are just lines providing at discrete time steps epoch of the state, the state (position in km, velocity in km/s) and the state derivative (with respect to time scale in days). Events Information File (EVTM Type) =================================== General Information about ESOC Events Information File ------------------------------------------------------ The EVTM type file contains the most up to date events consistent with the orbit data form ORHM and ORMM files. During the mission lifetime this file contained events up to the near future. The file archived in this data set contains the most up to date events as happened during all the mission phases (cruise and opperational orbits). For each event, one line of information is given. The events occur in ascending order in time. Event File Format ----------------- The following table shows a description of the collumns of the event file: _______________________________________________________________________ NAME | DESCRIPTION | --------|--------------------------------------------------------------| EVTTID | Event Type Identification | --------|--------------------------------------------------------------| EVTCNT | Event Count | --------|--------------------------------------------------------------| PREREC | Single character flag indicationg whether event is predicted | | ('P') or reconstituted ('R') | --------|--------------------------------------------------------------| EVTTIM | Start Time of Event in the format 'YY-DDDThh:mm:ss.dddZ' | --------|--------------------------------------------------------------| EVTDUR | Duration of event in seconds. | --------|--------------------------------------------------------------| EVTDES | Description of event. | --------|--------------------------------------------------------------| EVTTID is a alphanumeric string of lenght 4 which is unique for each event type. EVTCNT is a running number for each event type. It will always be in ascending consecutive order. The format of EVTTIM is 'YY-DDDThh:mm:ss.dddZ' where YY are the last two digits of the year, DDD is the day of the year and hh, mm, ss and ddd are hours, minutes, seconds and millisecons of the day. All other symbols are fixed character constants. The provided numerical accuracy of EVTTIM depends on the event type. For pericentre passages, the event time is provided with a numerical accuracy of 3 decimal digits. For all other events, the provided numerical accuracy is reduced to 1 second, i.e. the three decimal digits 'ddd' are '000'. EVTTIM is always given in UTC. If there is no duration related to the event (e.g. pericentre passage) then EVTTIM referes just to the time of the event rather than the start time of the event and EVTDUR contains 0. Although the end of events can be derived from the start time of the event and its duration, the end of the event is additionally given for convenience. In this case EVTTIM refers to the end of the event and EVTDUR contains also 0. Event Types in the file. ------------------------ The tables at the end of this section show all event types. The event types AxxH and LxxH refer to the event whenthe elevation of the line of sight from the Ground Station to the S/C rises above or falls below the horizon mask. The horizon mask defines, depending on the azimuth, the minimum required elevation of the antenna for reception of a signal. In the event description, the elevationof the horizon mask is given in degrees as 'nn'. The elevation for AxxH and LxxH may differ from each other. For the event types AxxH, AxxT, LxxH and LxxT the xx and XXX in the EVTTID and EVTDES indicate the Ground Station (G/S) antenna and complex as follows: _________________________________________ | xx | XXX | G/S Antenna | (EVTTID) | (EVTDES) | -------------------|----------|----------| Perth | 73 | PER | -------------------|----------|----------| New Norcia | 74 | NN0 | -------------------|----------|----------| Kourou | 75 | KOU | -------------------|----------|----------| DSN Goldstone 34m | 13 | GDS | -------------------|----------|----------| DSN Goldstone 70m | 14 | GDS | -------------------|----------|----------| DSN Goldstone 34m | 15 | GDS | -------------------|----------|----------| DSN Goldstone 34m | 24 | GDS | -------------------|----------|----------| DSN Goldstone 34m | 25 | GDS | -------------------|----------|----------| DSN Goldstone 34m | 26 | GDS | -------------------|----------|----------| DSN Madrid 34m | 54 | MAD | -------------------|----------|----------| DSN Madrid 34m | 61 | MAD | -------------------|----------|----------| DSN Madrid 70m | 63 | MAD | -------------------|----------|----------| DSN Madrid 34m | 65 | MAD | -------------------|----------|----------| DSN Canberra 34m | 34 | CAN | -------------------|----------|----------| DSN Canberra 34m | 42 | CAN | -------------------|----------|----------| DSN Canberra 70m | 43 | CAN | -------------------|----------|----------| DSN Canberra 34m | 45 | CAN | -------------------|----------|----------| The event types AxxH, AxxT, LxxH, LxxT indicate when the line of sight to the S/C reaches the given elevation at the G/S. These events do not indicate whether a TM/TC link is possible, as further events have to be consider like occultation, opposition or conjunction. The event types ALHM and LLHM refer to the event when the elevation of the line of sight from the lander to the S/C rises above or falls below the horizon mask. The horizon mask defines, depending on the azimuth, the minimum required elevation of the orbiter direction for reception of a signal. In the event description, the elevation of the horizon mask is given in degrees as 'nn'. In the beginning, the horizon mask is not known and 'nn' will always be zero. If a horizon mask derived from actual visibility times becomes available, it is used for this events. In that case, the elevation for ALHM and LLHM may differ from each other. AL10 and LL10 are given, when the elevation of the line of sight rises above and falls below 10 degrees. The entry 'XXX' in EVTDES of types ALHM, AL10, LLHM and LL10 gives the identification for the lander. BE2 is used for Beagle-2, MRA and MRB for Mars Exploration Rover A and Mars Exploration Rover B. The event types ALFn and ALRn refer to the event when the forward link (i.e. Mars Express Melacom to Beagle2) or return link (i.e. Beagle2 to Mars Express Melacom) become available and, at the same time, the aspect angles on both antennas (i.e. line of sight from Beagle2 to Mars Express with respect to Beagle2 antenna boresight and line of sight from Mars Express to Beagle2 with respect to Melacom antenna boresight) are below 70 degrees. Possible values for 'n' are 1 to 7 for the return link (2^n kbps) and 1 and 3 for the forward link. Event types LLFn and LLRn are the corresponding end events, i.e. correspond to the times when the forward or return links become unavailable. The events are computed based on a default S/C nadir poining attitude and on a Beagle2 antenna pointing direction towards the local zenith. In the events descriptions, bit rate in kbps (x=2, 4, 8, 18, 32, 64 and 128), range in Km (rrrrr) and line of sight direction from lander to S/C as azimuth in degrees (zzz.z) and elevation in degrees (ee.e) at the corresponding event time are provided. Type MOCS and MOCE refer to the event, when the line of sight from the centre of the Earth to the S/C starts and ends to be occulted by Mars. With MOCS some additional parameters are given: - rrr.rr,ddd.dd are right ascension form 0 to 360 and declination from -90 to +90 in degrees of the line of sight from the centre of the Earth to the S/C at start or end of occultation. - xxx.xx,yyy.yy are planetocentric longitude from 0 to 360 degrees eastward and planetocentric latitude from -90 to +90 degrees of the occulted Mars point. This is the point where the line of sight is tangential to the martian surface at start and end of occultation. - zzz is the Sun zenith angle in degrees for the occulted Mars point at start or end of occultation. Types MO2S and MO2E refer to the event, when the smallest distance between the surface of Mars and the line of sight from the centre of the Earth to the S/C drops below or rises above 200 km. Additional parameters are given: - rr.rr,dd.dd are right ascension and declination in degrees of the line of sight from the centre of the Earth to the S/C at event time. - xxx.xx,yyy.yy are planetocentric longitude from 0 to 360 degrees eastward and planetocentric latitude from -90 to +90 degrees of the point on the line of sight where the distance to the surface of Mars is 200 km. - zzz is the Sun zenith angle in degrees for that point at event time. Types LTCS and LTCE refer to the event, when the telecommand link between the G/S and the S/C is interrupted due an occultation by the Earth Moon. Types LTMS and LTME refer to the event, when the telemetry link is interrupted due an occultation by the Earth Moon. The G/S of the event is given as XXX in the event description with the same meaning as for the AOS/LOS events. Type POCS and POCE refer to the events, when the line of sight from the centre of the Earth to the S/C starts and ends to be occulted by the Mars Moon Phobos. Types DOCS and DOCE refer to the events, when the line of sight from the centre of the Earth to the S/C starts and ends to be occulted by the Mars Moon Deimos. For the computation of the evente, a spherical shape of the Mars Moons is assumed. The radius is an estimate of the semi major axis of the body ellipsoid (13.4 km for Phobos, 7.5 km for Deimos) augmented by an error radius of 30 km for Phobos and 100 km for Deimos to account for uncertainties in the moon's positions. For details on the computation of the events, see reference [TBD_1]. Types PENS and UMBS refer to the event, when the S/C enters the penumbra and umbra of the body indicated by xxx. The entry xxx can be either 'MAR' for Mars, 'PHO' for Phobos or 'DEI' for Deimos. The events PENE and UMBE indicate the exit from penumbra and umbra. For the computation of the events, a spherical shape is assumed. For Mars, the radius is equal to the equatorial radius of the ellipsoid. For Phobos and Deimos an augmented radius is used as defined in the description to the event types POCS, POCE, DOCS, DOCE (see above). Types SCDS and SCDE refer to the event, when the Sun/Earth/Spacecraft angle (SESC) falls below the limit where saf TM downlink is guaranteed. The nominal value for this estimate is 3 degrees according to refernce [TBD_2]. The actually used n value is provided in the event description This event type is provided on the G/S when the S/C is near the Earth. Far from the Earth, only one event type refering to the centre of the Earth has been provided. This is indicated by the acronym 'XXX' which is either a G/S (same definition as in the event description for acquisition and loss of signal is used) or 'EAR' for Earth. For details of the involved algorithms see reference [TBD_3]. Types SCUS, SOUS, SCUE and SOUE refer to the event, when the Sun/Spacecraft/Earth angle (SSCE) falls below the limit where safe TC uplink via HGA or MGA is guaranteed. The nominal value for this estimate is 5 degrees. The actually used value is provided in the event description. As for SCDS and SCDE, this event type is given either with respect to a G/S or the Earth depending on the S/C-Earth distance. The event types MPER and MAPO refer to the event when the S/C crosses the line of apsides. This event is defined by the time when the osculating true anomaly measured from -180 degrees to +180 degrees changes sign. For a detailed description of this event type refer to [TBD_4]. The number 'nnnn' in the event description provides the current orbit number. Orbit numbers are incremented by one with each apocentre passage starting from the first apocentre after orbit insertion. For each event of type MPER, also the subsatellite point (xxx.xx,yyy.yy) in planetocentric longitude from 0 to 360 degrees and planetocentric latitude between -90 and +90 degrees and the Sun zenith angle zz of the subsatellite point in degrees are given. Types KMDS and KMAS, 'x km descend' and 'x km ascend', refer to the event when the height of the S/C position above the Mars reference ellipsoid drops below or rises above x km. Events are provided for heights of 800 km, 1200 km, 2000 km and 4000 km (i.e. x i either '800', '1200', '2000' or '4000'). All events of type AxxH, LxxH, AxxT, LxxT, MOCS, MOCE, POCS, POCE, DOCS, DOCE, SCDS, SCDE, SCUS, SCUE, SOUS, SOUE refer to a purely geometrical situation. All considerations concerning related start and end times of TM and TC have to take into account additionally the one way light time. Types NPSS and NPNS indicate the times in the mission when the pointing of the x-axis has to switch from North to South (NPSS) or from South to North (NPNS) in order to avoid Sun incidence on the S/C -x face in nadir pointing mode around Mars. In nadir pointing mode, with the x-asis perpendicular to the ground track, the angle between the S/C -x axis and the Sun direction varies around the pericentre by some degrees (e.g. at the switching time around mid March 2004 about 5 degrees). This means that there is not a single data and time to switch to correct x axis pointing or, conversely, depending on the duration of the nadir pointing, it might therefore not be possible, to avoid Sun incidence on the S/C -x face during a complete pericentre passage in nadir pointing mode (neither with North nor with South pointing option). Instead, the duration of the nadir pointing has to be reduced or a small Sun incidence must be tolerated. The events are calculated as follows: At the beginning of the mission the S/C x axis was North pointing, i.e. close to the orbital North pole. The Sun incidence on the S/C -x face was the calculated at each pericenter assuming nadir pointing mode and the first pericentre is noted when the x axis has to switch from North to South pointing to avoid Sun incidence on the -x face exactly at pericentre. An event 'NPSS' is then inserted at the time of the preceding apocentre that indicates the required switch from North to South. The event 'NPNS' for switching back to North is inserted at the apocentre time before the pericentre where the switch back to North is required. Type EPSS indicates the date and time where the S/C y axis direction has to change from ecliptic North to South in order to minimise Sun incidence on the S/C +z face. There is a considerable time span around the switching time where a small Sun incidence angle can not be avoided, neither with North nor with South pointing option. The event is calculated such that the option with the smallest incidence angle is chosen. The computation of the event time is based on the direction of the ecliptic pole which is used by the AOCMS onboard software, not on the true ecliptic pole. Types NPSS, NPNS and EPSS refer only to the corresponding geometrical conditions as described above. The times may differ from the actual switching times as commanded by the Flight Control Team. _______________________________________________________________________ EVTTID | Event Type | --------|--------------------------------------------------------------| AxxH | Acquisition of Signal at ground station with elevation angle | | nn. | --------|--------------------------------------------------------------| AxxT | Acquisition of Signal 10 degrees at ground station. | --------|--------------------------------------------------------------| ALHM | Acquisition of signal at landing site from orbiter with | | elevation angle nn. | --------|--------------------------------------------------------------| AL10 | Acquisition of signal 10 degrees at landing site from orbiter| --------|--------------------------------------------------------------| ALFn | Acquisition of Beagle2 forward link with 2^n kbps. | --------|--------------------------------------------------------------| ALRn | Acquisition of Beagle2 return link with 2^n kbps. | --------|--------------------------------------------------------------| OMAS | Orbit Manoeuvre start | --------|--------------------------------------------------------------| SMAS | Slew manoeuvre start | --------|--------------------------------------------------------------| WOLS | Wheel offloading start | --------|--------------------------------------------------------------| FPAS | Entry into FPAP | --------|--------------------------------------------------------------| FPIS | Entry into FPIP | --------|--------------------------------------------------------------| MO2S | Mars Occultation 200 km start. | --------|--------------------------------------------------------------| MOCS | Mars occultation start | --------|--------------------------------------------------------------| POCS | Phobos occultation start | --------|--------------------------------------------------------------| DOCS | Deimos occultation start | --------|--------------------------------------------------------------| LTCS | Start of TC link interruption due to Earth Moon occultation | --------|--------------------------------------------------------------| LTMS | Start of TM link interruption due to Earth Moon occultation | --------|--------------------------------------------------------------| PENS | Penumbra start | --------|--------------------------------------------------------------| UMBS | Umbra start | --------|--------------------------------------------------------------| SCDS | S/C conjunction (SESC n degrees) start | --------|--------------------------------------------------------------| SCUS | S/C conjunction (SSCE n degrees) start | --------|--------------------------------------------------------------| SOUS | S/C opposition (SSCE n degrees) start | --------|--------------------------------------------------------------| KMDS | x km descend | --------|--------------------------------------------------------------| MPER | pericentre passage | --------|--------------------------------------------------------------| MAPO | apocentre passage | --------|--------------------------------------------------------------| LxxH | Loss of signal at ground station with elevation angle nn. | --------|--------------------------------------------------------------| LxxT | Loss of signal 10 degrees at ground station. | --------|--------------------------------------------------------------| LLHM | Loss of signal at landing site from orbiter with elevation | | angle nn. | --------|--------------------------------------------------------------| LL10 | Loss of signal 10 degrees at landing site from orbiter. | --------|--------------------------------------------------------------| LLFn | Loss of Beagle2 forward link with 2^n kbps | --------|--------------------------------------------------------------| LLRn | Loss of Beagle2 return link with 2^n kbps | --------|--------------------------------------------------------------| OMAE | Orbit manoeuvre end | --------|--------------------------------------------------------------| SMAE | Slew manoeuvre end | --------|--------------------------------------------------------------| WOLE | Wheel offloading end | --------|--------------------------------------------------------------| FPAE | exit from FPAP | --------|--------------------------------------------------------------| FPIE | exit from FPIP | --------|--------------------------------------------------------------| MOCE | Mars occultation end | --------|--------------------------------------------------------------| MO2E | Mars occultation 200 km end. | --------|--------------------------------------------------------------| POCE | Phobos occultation end | --------|--------------------------------------------------------------| DOCE | Deimos occultation end | --------|--------------------------------------------------------------| LTCE | End of TC link interruption due to Earth Moon occultation. | --------|--------------------------------------------------------------| LTME | End of TM link interruption due to Earth Moon occultation. | --------|--------------------------------------------------------------| UMBE | Umbra end. | --------|--------------------------------------------------------------| PENE | Penumbra end. | --------|--------------------------------------------------------------| SCDE | S/C conjunction (SESC n degrees) end. | --------|--------------------------------------------------------------| SCUE | S/C conjunction (SSCE n degrees) end. | --------|--------------------------------------------------------------| SOUE | S/C opposition (SSCE n degrees) end. | --------|--------------------------------------------------------------| KMAS | x km ascend. | --------|--------------------------------------------------------------| NPSS | x-axis pointing switch from North to South | --------|--------------------------------------------------------------| NPNS | x-axis pointing switch from South to North | --------|--------------------------------------------------------------| EPSS | y-axis pointing switch from North to South | --------|--------------------------------------------------------------| _______________________________________________________________________ EVTTID | EVTDES | --------|--------------------------------------------------------------| AxxH | XXX_AOS_nn | --------|--------------------------------------------------------------| AxxT | XXX_AOS_10 | --------|--------------------------------------------------------------| ALHM | xxx_AOS_nn | --------|--------------------------------------------------------------| AL10 | xxx_AOS_10 | --------|--------------------------------------------------------------| ALFn | BE2_AOS_TC_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| ALRn | BE2_AOS_TM_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| OMAS | ORB_MAN_START | --------|--------------------------------------------------------------| SMAS | SLEW_MAN_START | --------|--------------------------------------------------------------| WOLS | WHEEL_OFFL_START | --------|--------------------------------------------------------------| FPAS | FPAP_START | --------|--------------------------------------------------------------| FPIS | FPIP_START | --------|--------------------------------------------------------------| MO2S | OCC_MARS_200KM_START_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| MOCS | OCC_MARS_START_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| POCS | OCC_PHOBOS_START | --------|--------------------------------------------------------------| DOCS | OCC_DEIMOS_START | --------|--------------------------------------------------------------| LTCS | XXX_OCC_MOON_TC_START | --------|--------------------------------------------------------------| LTMS | XXX_OCC_MOON_TM_START | --------|--------------------------------------------------------------| PENS | xxx_PENUMBRA_START | --------|--------------------------------------------------------------| UMBS | xxx_UMBRA_START | --------|--------------------------------------------------------------| SCDS | XXX_CON_START_SESC_n | --------|--------------------------------------------------------------| SCUS | XXX_CON_START_SSCE_n | --------|--------------------------------------------------------------| SOUS | XXX_OPP_START_SSCE_n | --------|--------------------------------------------------------------| KMDS | x_KM_DESCEND | --------|--------------------------------------------------------------| MPER | PERICENTRE_PASSAGE_nnnn_/_SSP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| MAPO | APOCENTRE_PASSAGE_nnnn | --------|--------------------------------------------------------------| LxxH | XXX_LOS_nn | --------|--------------------------------------------------------------| LxxT | XXX_LOS_10 | --------|--------------------------------------------------------------| LLHM | xxx_LOS_nn | --------|--------------------------------------------------------------| LL10 | xxx_LOS_10 | --------|--------------------------------------------------------------| LLFn | BE2_LOS_TC_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| LLRn | BE2_LOS_TM_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| OMAE | ORB_MAN_END | --------|--------------------------------------------------------------| SMAE | SLEW_MAN_END | --------|--------------------------------------------------------------| WOLE | WHEEL_OFFL_END | --------|--------------------------------------------------------------| FPAE | FPAP_END | --------|--------------------------------------------------------------| FPIE | FPIP_END | --------|--------------------------------------------------------------| MOCE | OCC_MARS_END_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| MO2E | OCC_MARS_200KM_END_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| POCE | OCC_PHOBOS_END | --------|--------------------------------------------------------------| DOCE | OCC_DEIMOS_END | --------|--------------------------------------------------------------| LTCE | XXX_OCC_MOON_TC_END | --------|--------------------------------------------------------------| LTME | XXX_OCC_MOON_TM_END | --------|--------------------------------------------------------------| UMBE | xxx_UMBRA_END | --------|--------------------------------------------------------------| PENE | xxx_PENUMBRA_END | --------|--------------------------------------------------------------| SCDE | XXX_CON_END_SESC_n | --------|--------------------------------------------------------------| SCUE | XXX_CON_END_SSCE_n | --------|--------------------------------------------------------------| SOUE | XXX_OPP_END_SSCE_n | --------|--------------------------------------------------------------| KMAS | x_KM_ASCEND | --------|--------------------------------------------------------------| NPSS | NADIR_POINTING_X_N_TO_S_SWITCH | --------|--------------------------------------------------------------| NPNS | NADIR_POINTING_X_S_TO_N_SWITCH | --------|--------------------------------------------------------------| EPSS | EARTH_POINTING_Y_N_TO_S_SWITCH | --------|--------------------------------------------------------------| _______________________________________________________________________ EVTTID | Duration until | --------|--------------------------------------------------------------| AxxH | XXX_LOS_nn | --------|--------------------------------------------------------------| AxxT | XXX_LOS_10 | --------|--------------------------------------------------------------| ALHM | xxx_LOS_nn | --------|--------------------------------------------------------------| AL10 | xxx_LOS_10 | --------|--------------------------------------------------------------| ALFn | BE2_LOS_TC_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| ALRn | BE2_LOS_TM_xKBPS_/_RN_rrrrr_/_AZ_zzz.z_/_ELV_ee.e | --------|--------------------------------------------------------------| OMAS | ORB_MAN_END | --------|--------------------------------------------------------------| SMAS | SLEW_MAN_END | --------|--------------------------------------------------------------| WOLS | WHEEL_OFFL_END | --------|--------------------------------------------------------------| FPAS | FPAP_END | --------|--------------------------------------------------------------| FPIS | FPIP_END | --------|--------------------------------------------------------------| MO2S | OCC_MARS_200KM_END_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| MOCS | OCC_MARS_END_/_RA_rrr.rr_/_DE_ddd.dd_/_ | | OMP_(xxx.xx,yyy.yy)_/_SZA_zzz | --------|--------------------------------------------------------------| POCS | OCC_PHOBOS_END | --------|--------------------------------------------------------------| DOCS | OCC_DEIMOS_END | --------|--------------------------------------------------------------| LTCS | XXX_OCC_MOON_TC_END | --------|--------------------------------------------------------------| LTMS | XXX_OCC_MOON_TM_END | --------|--------------------------------------------------------------| PENS | xxx_PENUMBRA_END | --------|--------------------------------------------------------------| UMBS | xxx_UMBRA_END | --------|--------------------------------------------------------------| SCDS | XXX_CON_END_SESC_n | --------|--------------------------------------------------------------| SCUS | XXX_CON_END_SSCE_n | --------|--------------------------------------------------------------| SOUS | XXX_OPP_END_SSCE_n | --------|--------------------------------------------------------------| KMDS | x_KM_ASCEND | --------|--------------------------------------------------------------| MPER | n/a | --------|--------------------------------------------------------------| MAPO | n/a | --------|--------------------------------------------------------------| LxxH | n/a | --------|--------------------------------------------------------------| LxxT | n/a | --------|--------------------------------------------------------------| LLHM | n/a | --------|--------------------------------------------------------------| LL10 | n/a | --------|--------------------------------------------------------------| LLFn | n/a | --------|--------------------------------------------------------------| LLRn | n/a | --------|--------------------------------------------------------------| OMAE | n/a | --------|--------------------------------------------------------------| SMAE | n/a | --------|--------------------------------------------------------------| WOLE | n/a | --------|--------------------------------------------------------------| FPAE | n/a | --------|--------------------------------------------------------------| FPIE | n/a | --------|--------------------------------------------------------------| MOCE | n/a | --------|--------------------------------------------------------------| MO2E | n/a | --------|--------------------------------------------------------------| POCE | n/a | --------|--------------------------------------------------------------| DOCE | n/a | --------|--------------------------------------------------------------| LTCE | n/a | --------|--------------------------------------------------------------| LTME | n/a | --------|--------------------------------------------------------------| UMBE | n/a | --------|--------------------------------------------------------------| PENE | n/a | --------|--------------------------------------------------------------| SCDE | n/a | --------|--------------------------------------------------------------| SCUE | n/a | --------|--------------------------------------------------------------| SOUE | n/a | --------|--------------------------------------------------------------| KMAS | n/a | --------|--------------------------------------------------------------| NPSS | n/a | --------|--------------------------------------------------------------| NPNS | n/a | --------|--------------------------------------------------------------| EPSS | n/a | --------|--------------------------------------------------------------| Star Occultations File (STOM Type) ================================== For a list of stars provided by the SPICAM experiment, star occultation events are given in a separate file. Four types of events are considered: - 200 km descend This event refers to the time when the minimum distance of the line of sight between S/C and star from the Mars reference ellipsoid drops below 200 km. - start occultation This event refers to the time when the line of sight starts to be occulted by the Mars reference ellipsoid. - end occultation This event refers to the time when the line of sight ends to be occulted by the Mars reference ellipsoid. - 200 ascend This event refers to the event when the minimum distance of the line of sight between S/C and star from the Mars reference ellipsoid rises above 200 km. All events are sorted in ascending order in time. For each event one line of description is given. The meaning of each collumn in the star occultation is as follows _______________________________________________________________________ Collumn | Field description | =========|=============================================================| 1 | Orbit number, counted from first apocentre after orbit | | insertion. | ---------|-------------------------------------------------------------| 2 | Event time in UTC in the format YY-DDDThh:mm:ssZ (for the | | format description, please refer to the EVTTIM parameter in | | the previous section of this document) | ---------|-------------------------------------------------------------| 3 | Time until next pericentre in the format hh:mm:ss | ---------|-------------------------------------------------------------| 4 | Time since last pericentre in the format hh:mm:ss | ---------|-------------------------------------------------------------| 5 | True anomaly in degrees between -180 and +180 degrees. | ---------|-------------------------------------------------------------| 6 | Bright Star Catalogue star number | ---------|-------------------------------------------------------------| 7 | Event description, one of the following four entries: | | 200 km, descending | | start occultation | | end occultation | | 200 km, ascending | ---------|-------------------------------------------------------------| 8 | Occultation point in the format (xxx.xx,yyy.yy) where | | xxx.xx is planetocentric longitude in degrees from 0 to 360 | | eastward, and yyy.yy is planetocentric latitude in degrees | | from -90 to +90 degrees. | ---------|-------------------------------------------------------------| 9 | Solar zenith angle, i.e. the angular separation in degrees | | between the Sun direction and the direccion of the | | occultation point as seen from the centre of Mars. | ---------|-------------------------------------------------------------| 10 | Local time, i.e. the difference in longitude in degrees | | between occultation point and Sun direction from -180 to | | +180 degrees. | ---------|-------------------------------------------------------------| For the format definition of the collumns, please refer to the product label of the star occultation files. For a detailed description of relevant algorithms and model assumptions (e.g. reference ellipsoid, rotational elements) refer to [TBD_5].