#****************************************************************************# #- Table of contents ##TOC #****************************************************************************# #- 1 Data products #- 1.1 The TRAL itself #- 1.2 SPICE kernels #- 1.3 Files for MAPPS #- 1.4 Miscellaneous #- 2 LTP 4 #- 2.1 Robust case #- 2.1.1 Candidate 1 #- 2.1.2 Candidate 2 #- 2.1.3 Candidate 3 #- 2.1.4 Candidate 4 #- 2.2 Preferred case #- 2.2.1 Candidate 1 #- 2.2.2 Candidate 2 #- 2.2.3 Candidate 3 #- 2.2.4 Candidate 4 #- 2.2.5 Candidate 5 #- 2.2.6 Candidate 6 #- 2.2.7 Candidate 7 #- 3 LTP 5 #- 3.1 Robust case #- 3.1.1 Candidate 1 #- 3.1.2 Candidate 2 #- 3.1.3 Candidate 3 #- 3.2 Preferred case #- 3.2.1 Candidate 1 #- 3.2.2 Candidate 2 #- 3.2.3 Candidate 3 #- 3.2.4 Candidate 4 #- 4 LTP 6 #- 4.1 Robust case #- 4.1.1 Candidate 1 #- 4.1.2 Candidate 2 #- 4.1.3 Candidate 3 #- 4.1.4 Candidate 4 #- 4.2 Preferred case #- 4.2.1 Candidate 1 #- 4.2.2 Candidate 2 (NEW 2015-02-24) #****************************************************************************# #- 1 ## Data products #****************************************************************************# Note: Not all the products are present for all candidate trajectories. #============================================================================# #- 1.1 ### The TRAL itself #============================================================================# .ROS: The actual TRAL file to be submitted to FDyn. .ROS.xml: A copy of the abouve with appended file extension to facilitate the display in XML viewers. #============================================================================# #- 1.2 ### SPICE kernels #============================================================================# .bsp: Spacecraft position kernel for an approximate trajectory. _bridge.bsp: Spacecraft position kernel which allows to link the trajectory defined in the TRAL seamlessly to the pre-landing trajectory. _nadir.bc: Camera kernel providing VIRTIS-H pointing nadir with power optimised attitude. _FDyn.bsp: Spacecraft position kernel for an exact trajectory created by Flight Dynamics. _FDyn_nadir.bc: Camera kernel providing VIRTIS-H pointing nadir with power optimised attitude for an exact trajectory created by Flight Dynamics. #============================================================================# #- 1.3 ### Files for MAPPS #============================================================================# Note: For newer TRALs which follow (more or less) the naming convention, the dat/def/evt/gsv are not appended to the TRAL name (as shown below), but inserted to replace three underscores before H or P. _dat.asc: Approximate trajectory in MAPPS format. _def.orb: Orbit definition file in MAPPS format. _evt.orb: Event file in MAPPS format to be used together with the orbit definition file. _gsv.asc: Ground station visibility file in MAPPS format. #============================================================================# #- 1.4 ### Miscellaneous #============================================================================# _oem.txt: Approximate trajectory in ESOC ASCII format; this file is submitted to FDyn together with the TRAL for cross checking. _body_fixed.asc: Approximate trajectory in the body fixed frame in MAPPS like format, but with UTC instead of JD times; requested by CONSERT. _man_log.txt: Manoeuvre log with short descriptions of all arcs and Delta-v estimations; submitted to FDyn together with the TRAL for cross checking. _pointing_error.dat: ASCII table with pointing errors. The first column gives the pointing error relevant for navigation (knowledge on ground, reset at data cut-off), the second column gives the actual on-board error (reset at uplink completed), which is relevant for instrument operations. #****************************************************************************# #- 2 ## LTP 4 #****************************************************************************# Time range: From 2014-11-19T01:00:00 to 2015-03-11T01:00:00 #============================================================================# #- 2.1 ### Robust case #============================================================================# Comet activity: Maximum #----------------------------------------------------------------------------# #- 2.1.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c1_H Updated: 2014-03-14 This candidate trajectory is based on v19 of the HAC trajectory requirements spreadsheet. This version is much more optimised than the one submitted for the end-to-end test. A fact that caused some dispute is that the time needed for transition from the bound orbit to the first fly-by is taken from the bound orbit time. There is an additional one month SPK (with `_bridge' in the name). It can be used to seamlessly connect the LTP 4 trajectory to the FDyn pre-landing trajectory by loading (in the given sequence): 1. RORL_DL_001_01_______00001.bsp 2. TRAL_DL_004_01_c1_H.bsp 3. TRAL_DL_004_01_c1_H_bridge.bsp This TRAL was sent to FDyn for processing in order to get the trajectory on the FDyn server for attitude checks. On 2014-03-14, all products for this case were updated based on the newer comet orbit SPK CORL_DL_001_01____A__00001.BSP (Before, ORHW_121217_CompleteTrajectory_comet.bsp had been used). In addition, there were some particular updates and additions: TRAL_DL_004_01_c1_H.ROS: The TRAL does now comprise the assumed activity level in the header. TRAL_DL_004_01_c1_H_def.orb: Previously, the orbit definition was based on the actual orbits (in the case of bound orbits) and on actual TRAL arcs (in the case of fly-bys). Now, it is strictly based on VSTP cycles. TRAL_DL_004_01_c1_H_evt.orb: This file had not been provided previously. TRAL_DL_004_01_c1_H_gsv.asc: Previously, only the visibility for NNO was listed. Now, visibilities for NNO, CEB, MLG, MAD, CAN, and GDS are listed. TRAL_DL_004_01_c1_H_pointing_error.dat: Previously, the pointing error in bound orbits did not take into account manoeuvre errors. Now, manoeuvres to maintain the orbit are considered. Previously, the navigation relevant pointing error was propagated until Friday, although nominal data cut off is on Thursday, to have one day margin. As has been agreed for bound orbits, the error is now only integrated until Thursday. All this is not really relevant for the HAC, as the pointing errors in the bound orbit are anyway beyond the threshold. #----------------------------------------------------------------------------# #- 2.1.2 #### Candidate 2 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c2_H This trajectory is very similar to candidate 1 (TRAL_DL_004_01_c1_H). The only difference is that the first fly-by starts on 2014-01-20 instead of 2014-01-17 and consequently the spacecraft stays three days longer in bound orbit. The former first fly-by has just been removed, so the fly-by sequence starts with the former second fly-by. The trajectory has only changed between 2014-12-10T01:00 and 2014-12-20T01:00. Outside of this time window, it is exactly the same as TRAL_DL_004_01_c1_H. #----------------------------------------------------------------------------# #- 2.1.3 #### Candidate 3 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c3_H Creation date: 2014-06-27 This version differs from candidate 2 in the following points: The close fly-bys are now implemented as case A fly-bys, i.e., the closest approach point (in Keplerian approximation) is exactly over the subsolar point and in the TRAL the flyoverdirection (the VSTP target point, where position errors vanish) is also over the subsolar point. The close fly-by in MTP013 has been lowered from 10 to 8 km distance. The lateral one day arcs which follow the close fly-bys have been optimised for Delta-v. MTP010 has been moved from LTP004 to LTP003. Therefore, the TRAL does now start with MTP011. However, all trajectory related products still comprise MTP010 (they even start three days earlier than the start time of MTP010). At the end, the trajectory extends one day beyond the end of LTP004. The last far fly-by continues with constant velocity for one more day (beyond the end point specified in the TRAL). #----------------------------------------------------------------------------# #- 2.1.4 #### Candidate 4 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01____H__00001.ROS Creation date: 2014-09-12 This version differs from candidate 3 in the following points: To account for the opposite sense of comet rotation, the trajectory is mirrored +y <---> -y as described for the preferred case in section #2.2.6#. Because the mirroring is performed in the slowly rotating Sun-spin frame, a few small adjustments were needed to stay within trajectory constraints. It was found that with the foreseen continuation in LTP005, a constraint violation would occur in the case of a manoeuvre interruption just at the boundary between LTP004 and LTP005. In order to avoid this, the return arc after the last closeFB in LTP004 was modified. The first two farFBs were removed to allow more time for transition from bound orbit, which may be needed in the case of a disadvantages sense of rotation of the orbit. The TRAL does now start on 2014-12-27. The first closeFB was lowered from 10 to 8 km, with respective increase of fly-by velocity. It was also shifted by 12 hours to be compatible with the MOC schedule around New Year's Eve. #============================================================================# #- 2.2 ### Preferred case #============================================================================# #----------------------------------------------------------------------------# #- 2.2.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c1_L Comet activity: 100 % LAC This candidate trajectory is based on the LAC trajectory requirements spreadsheet from_2013-Jun-27. For deciding whether a bound orbit is navigatable, only the gas drag error was considered. Manoeuvre errors from changing and maintaining a bound orbit were not taken into account. However, the effects of manoeuvres in bound orbits are almost exactly compensated by respective mitigation measures, so the trajectory is still valid with respect to pointing errors. For the transition from bound orbits to the start point of the first fly-by and back from the end point of the last fly-by to bound orbit, four and three days, respectively, were assumed. #----------------------------------------------------------------------------# #- 2.2.2 #### Candidate 2 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c2_L Comet activity: 100 % LAC The purpose of this version was to extend the transition times from bound orbits to the start point of the first fly-by and back from the end point of the last fly-by to bound orbit to one week each, which is a more realistic assumption than the previously used value of about half a week. This seemingly minor change triggered a few other modifications. As the bound orbit is now left at a different time and hence at a different orbital phase, it was more Delta-v efficient to reverse the direction of the fly-bys. The return to bound orbit from the opposite direction suggested --- also for Delta-v efficiency --- the swap of morning and afternoon orbit. For assessing the navigability of bound orbits, maintenance manoeuvres were assumed once per week on Wednesday, and then the error was only propagated until the nominal data cut-off on Thursday, as agreed with FDyn for the case of bound orbits. #----------------------------------------------------------------------------# #- 2.2.3 #### Candidate 3 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c3_L Comet activity: 100 % LAC Creation date: 2014-04-01 This trajectory represents the ``11 weeks bound orbits'' option. The first eight weeks are identical to candidate 2, however, while candidate 2 leaves the bound orbits after eight weeks for a close and a far subsolar fly-by, this trajectory stays three more weeks on a bound orbit (tilt towards afternoon) and then leaves for similar fly-bys. After the subsolar fly-bys, dayside far fly-bys are inserted until the end of the LTP. The assumptions on orbit maintenance manoeuvres are the same as for candidate 2. #----------------------------------------------------------------------------# #- 2.2.4 #### Candidate 4 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c4_L Comet activity: 100 % LAC Creation date: 2014-04-11 Updated: 2014-05-13 This trajectory is another representation of the ``11 weeks bound orbits'' option. The difference to candidate 3 is that orbit maintenance manoeuvres are assumed two times per week, not only on Wednesday but also on Saturday. However, the assumed error of such manoeuvres is reduced from 0.5 cm/s to 0.25 cm/s. The previously applied waiver that for the short (3 days) VSTP the pointing error has only to be propagated until nominal data cut-off and not one day more (as stated in the trajectory ICD) is not used anymore. Because of the different orbit radii, the final orbit phase is different from candidate 3. For a Delta-v efficient transition to the first fly-by, the orientation of the fly-by part has been rotated by 180 deg around the axis to the Sun. A few other modifications have been applied to the day side legs after the subsolar fly-bys. On 2014-05-13, all products for this case were updated. There were two changes: First, while in the previous version, the target point of the close fly-by (`flyoverepoch' and `flyoverdirection' in the TRAL) was chosen to be the closest approach point (in Keplerian approximation), this target point is now chosen to be at the minimum phase angle. The purpose of this change was to minimise the LTP to STP position error at minimum phase angle to facilitate the implementation of a spacecraft flip. This change does not affect the approximate trajectory (as provided here), but the actual trajectory provided by FDyn may be slightly different. Second, in order to facilitate import into MAPPS and ASPEN, the trajectory was extended by one day beyond the LTP time range at the beginning and at the end. At the beginning, a 30 km radius terminator orbit was assumed for the extra day (although according to the current FDyn trajectory, the spacecraft will not yet be in that orbit one day earlier). At the end, the last far fly-by was just continued with constant velocity for one more day (beyond the end point specified in the TRAL). #----------------------------------------------------------------------------# #- 2.2.5 #### Candidate 5 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01_c5_L Comet activity: 100 % LAC Creation date: 2014-07-17 This version differs from candidate 4 in the following points: The close fly-bys are now implemented as case A or case B fly-bys, i.e., the closest approach point (in Keplerian approximation) is exactly over the subsolar point or over the point of minimum phase angle, respectively, and in the TRAL the flyoverdirection (the VSTP target point, where position errors vanish) is pointing to this point. The close fly-by in MTP013 has been lowered from 10 to 8 km distance. In the TRAL header, there is a comment envisaging a phasing request for that close fly-by. The parameters of close fly-bys are now written with extremely high precision in the TRAL. This is to facilitate SGS internal double checking, as it is needed to exactly reconstruct the fly-by trajectory (in Keplerian approximation). The lateral one day arcs which follow the close fly-bys have been optimised for Delta-v. MTP010 has been moved from LTP004 to LTP003. Therefore, the TRAL does now start with MTP011. However, all trajectory related products still comprise MTP010 (they even start three days earlier than the start time of MTP010). At the end, the trajectory extends seven weeks beyond the end of LTP004 into LTP005. #----------------------------------------------------------------------------# #- 2.2.6 #### Candidate 6 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_01____P__00002.ROS Comet activity: 24 % HAC Creation date: 2014-09-08 Updated: 2014-09-16 This version differs from candidate 5 in the following points: The measured comet mass corresponding to GM = 6.6e2 m^3/s^2 is used. The directly observed comet rotation is used. The orientation of the rotation axis is close to the previously assumed one, but the sense of rotation is the opposite. As the trajectory is defined in the SUN_SPIN frame, this yields a rotation by 180 deg around the x-axis of the frame. To preserve summer and winter pole views, the trajectory is mirrored +z <---> -z. These two operations (rotation and z-mirroring) can more easily be described by just mirroring +y <---> -y. Note that only fly-bys have been mirrored this way; the sense of rotation of the spacecraft orbit around the comet is the same as before. The first farFB after the bound orbit phase (which is a preparation arc for a subsequent subsolar closeFB) has been z-mirrored so that its angular momentum relative to the comet is not oppositely to the bound orbit angular momentum. The bound orbit and the close fly-by have been retuned to obey pointing error constraints under the assumption of 24 % of HAC activity uncertainty. The bound orbit was raised from 24 km to 28 km, the velocity of the fly-by was slightly increased while keeping the fly-by distance of 8 km. At the end, the trajectory extends one day beyond the end of LTP004. On 2014-09-16, two files (TRAL_DL_004_01_c6_L_def.orb and TRAL_DL_004_01_c6_L_evt.orb) were updated to reflect the modified VSTP start and end times around Christmas 2014. #----------------------------------------------------------------------------# #- 2.2.7 #### Candidate 7 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_004_02____P__00003.ROS Comet activity: 24 % HAC Creation date: 2014-09-24 The RMOC counter in the file name has been increased from 01 to 02, as this will be submitted to RMOC together with candidate 6. Still, the comet mass corresponding to GM = 6.6e2 m^3/s^2 is used instead of the latest measurement of 6.67 to be consistent with c7 and the HAC version. This version differs from candidate 6 in the following points: The sense of the bound orbits has been reversed from prograde to retrograde. Orbit transitions have been adapted. The direction of the first farFB (preparation of the following closeFB) has been reversed. The orbit is left four days earlier to get a nice transition. #****************************************************************************# #- 3 ## LTP 5 #****************************************************************************# Time range: From 2015-03-11T01:00:00 to 2015-07-01T01:00:00 #============================================================================# #- 3.1 ### Robust case #============================================================================# Comet activity: Maximum #----------------------------------------------------------------------------# #- 3.1.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_01_c1_H This candidate trajectory is based on v19 of the HAC trajectory requirements spreadsheet. This version is much more optimised than the one submitted for the end-to-end test. The trajectory files start one day before the start time of the first leg in the TRAL in order to fully encompass the first manoeuvre. #----------------------------------------------------------------------------# #- 3.1.2 #### Candidate 2 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_01____H__00004 Comet activity: 100 % HAC Creation date: 2014-10-28 This version differs from candidate 1 in the following points: The actual comet rotation is used. The trajectory is mirrored to account for the different sense of rotation. The closeFBs are implemented as case B. The co-rotational closeFB is targeted at 90 deg W. The polar closeFB has CAP over the pole. The end was modified to tie to subsequent terminator farFBs. Modifications of cut-off, uplink, and manoeuvre times according to the ESOC holiday schedule have been implemented. The trajectory files start one week earlier with the last arc of LTP004 and extend one day beyond the end of LTP005 by linear extrapolation. #----------------------------------------------------------------------------# #- 3.1.3 #### Candidate 3 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_02____H__00008 Comet activity: 100 % HAC Creation date: 2015-02-03 This version was created outside of the regular delivery schedule to deal with a reaction wheel problem which required a shift of manoeuvres from MTP016 onwards. It differs from candidate 2 in the following points: The leap second on 2015-06-30 is now handled correctly, i.e., the arc in which is lies is one second longer. All manoeuvres from MTP016 onwards are pushed backward in time by 40 minutes. This required to increase the velocity of the polar closeFB in MTP016 by 1 cm/s. #============================================================================# #- 3.2 ### Preferred case #============================================================================# #----------------------------------------------------------------------------# #- 3.2.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_01_c1_L This candidate trajectory is based on the LAC trajectory requirements spreadsheet from_2013-Jun-27. The trajectory files start one day before the start time of the first leg in the TRAL in order to fully encompass the first manoeuvre. #----------------------------------------------------------------------------# #- 3.2.2 #### Candidate 2 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_01____P__00005 Comet activity: 125 % LAC Creation date: 2014-10-30 This version differs from candidate 1 in the following points: The trajectory was rotated to match a respective rotation in LTP004, which was introduced before the mirroring because of comet rotation came into play; then it was mirrored in addition. A comet mass corresponding to GM = 6.66e2 m^3/s^2 is used. The trajectory was tuned to 125 % LAC. The closeFBs are implemented as case B. The bound orbits in MTP014 are replaced by farFBs and a closeFB. MTP016 is adapted to accommodate a co-rotational closeFB instead of the the N-S closeFB. This required also changes at the end of MTP015 and the beginning of MTP017. The return arcs of closeFBs have been modified either to avoid constraint violations that came up because of closeFB modifications or to optimize for Delta-v. The trajectory files start four days earlier with the last arc of LTP004 and extend one day beyond the end of LTP005 by linear extrapolation. #----------------------------------------------------------------------------# #- 3.2.3 #### Candidate 3 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_01____P__00006 Comet activity: 125 % LAC Creation date: 2014-11-12 This version differs from candidate 2 in the following points: A comet mass corresponding to GM = 6.665e2 m^3/s^2 is used. The latest comet attitude file (CATT) was plugged in. The co-rotational closeFB in MTP016 was tuned to have CAP at 105 degree Eastern longitude. This caused modifications of the two subsequent arcs and a very minor modification of the preceding arc. #----------------------------------------------------------------------------# #- 3.2.4 #### Candidate 4 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_005_02____P__00007 Comet activity: 125 % LAC Creation date: 2015-02-03 This version was created outside of the regular delivery schedule to deal with a reaction wheel problem which required a shift of manoeuvres from MTP016 onwards. It differs from candidate 3 in the following points: The leap second on 2015-06-30 is now handled correctly, i.e., the arc in which is lies is one second longer. All manoeuvres from MTP016 onwards are pushed backward in time by 40 minutes. This required to increase the velocity of the closeFB in MTP017 by 1 cm/s. Because of the later manoeuvre, the CAP of the corotational closeFB in MTP016 would move from longitude 105E to 86E. The latest CATT file then brings CAP to 141E. This is longitude wise in the centre of the flat target area, therefore it is left like that and the closeFB distance and velocity are unchanged from the previous version. #****************************************************************************# #- 4 ## LTP 6 #****************************************************************************# Time range: From 2015-07-01T01:00:00 to 2015-10-21T01:00:00 #============================================================================# #- 4.1 ### Robust case #============================================================================# Comet activity: Maximum #----------------------------------------------------------------------------# #- 4.1.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01_c1_H Creation date: 2014-02-19 This candidate trajectory is based on v19 of the HAC trajectory requirements spreadsheet. The trajectory files start one day before the start time of the first leg in the TRAL in order to fully encompass the first manoeuvre. This trajectory contains a far excursion. As agreed with FDyn, a request to reduce the number of navigation slots when very far from the comet was written in the TRAL header. The MAPPS orbit definition file and the event file that comes with it (by the way: this event file is for the first time provided with this delivery) are now strictly based on VSTP cycles, not any more an actual arcs. The Delta-v consumption of this trajectory is rather high: 34.61 m/s. #----------------------------------------------------------------------------# #- 4.1.2 #### Candidate 2 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01____H__00009 Creation date: 2014-11-28 This trajectory has not very much to do with the previous version, as from LTP006 onward, HAC and preferred case shall be aligned as much as possible. The new common segmentation is still to be determined. This is just a first draft version which consists only of farFBs. There are not yet any closeFBs and also the far excursion planned for LTP006 is not yet implemented. The purpose of this trajectory is to demonstrate the farFB pattern, which is chosen in a regular way so that farFBs can be replaced by closeFBs which seamlessly connect to the pattern before and after. In MTP018, the farFBs are in the terminator plane, in MTP019-021 they are on the dayside, going down to the minimum phase angle of 50 deg. #----------------------------------------------------------------------------# #- 4.1.3 #### Candidate 3 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01____H__00010 Creation date: 2014-12-18 This version differs from candidate 2 in the following points: The latest comet attitude file (CATT) was plugged in. According to the segmentation agreed at SWT#39, three closeFBs have been plugged in (there is a fourth one in the segmentation, but it was designated to be replaced by a farFB in the HAC if Delta-v expense is large, and it is). The closeFBs where set to a velocity of 3 m/s and the distance was tuned to stay within pointing error constraints. The far excursion was implemented in MTP021 based on the design in candidate 1. However, there are differences in the details. In the Sun-spin frame, the excursion goes now into the opposite direction, but as the Sun-spin frame was rotated upside down because of the actual comet spin axis, the excursion goes in about the same direction as before. The whole excursion has been brought forward in time by one week to complete it including full return within LTP006. As implemented now, the excursion fits well in the regular farFB pattern of LTP006. #----------------------------------------------------------------------------# #- 4.1.4 #### Candidate 4 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01____H__00012 Creation date: 2015-02-11 This version differs from candidate 3 in the following points: The leap second on 2015-06-30 is properly taken into acount (this is before the start of LTP006, but it affects the preceding arc which is comprised in the trajectory related products). The MTP018a closeFB is implemented as phasable, i.e., the farFBs before and after are modified to make everything robust against a shift of up to 12 hours. The preparation arc of the closeFB in MTP019a and the farFBs in MTP019b have slightly been re-tuned. One farFB arc in MTP019b is shifted from day side to night side, the same one as in the preferred case. The preceding lateral arc had to be re-tuned to avoid the forbidden night cone. The dayside farFB in MTP021 just before the far excursion has been re-tuned to allow the excursion to go closer to the minimum phase angle. The return from the far excursion is implemented similarly to the Preferred case with two in line arcs. All manoeuvres are time shifted by 40 minutes (as required because of the reaction wheel problem). This shift from MTP016 onwards had very slightly changed the end point of LTP005, so the start point of LTP006 had to be adapted. Because of the manoeuvre time shift, the last closeFB had to be slightly modified. The latest CORB and CATT (00138) are plugged in. The phasing of the closeFB in MTP018 was tuned to hit Imhotep jet. A shift of -5161 seconds is required. The jet is then hit at 2015-07-11T04:38:37. All files are available for three cases, distinguished by an extra letter directly after the ``H'' denoting the HAC. The three cases are: N: No phasing, manoeuvre at the nominal time of 01:40:00. M: Maximum phasing, manoeuvre 12 hours earlier at 13:40:00. O: Optimized phasing, manoeuvre 5161 seconds earlier at 00:13:59. #============================================================================# #- 4.2 ### Preferred case #============================================================================# #----------------------------------------------------------------------------# #- 4.2.1 #### Candidate 1 #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01____P__00011 Comet activity: 125% LAC Creation date: 2015-01-12 As from LTP006 onward, HAC and preferred case shall be aligned as much as possible, this preferred case TRAL is based on TRAL_DL_006_01____H__00010. It differs from the HAC TRAL in the following points: Everything is tuned for the preferred case activity of LTP005, i.e., 125% LAC. The closeFBs are set to a distance of 15 km and the velocity is tuned appropriately. The farFB at the beginning of MTP19b was moved to the night side. An additional afternoon closeFB was inserted in the second week of MTP019b. The velocity is fixed to 2 m/s and the distance is tuned to fulfil the pointing error constraints. The two arcs which comprise the return from the far excursion are now exactly in line; only the velocity changes at the manoeuvre connecting them. The return after the activity campaign closeFB in MTP018a is now done in two steps with the connection point moved a little bit away from the comet in order to make it robust against a time shift of 0-12 hours of the closeFB. The preparation arc is tuned for the worst case of 12 hour shift. The activity campaign closeFB itself is tuned to go through the jet from the Imhotep region, based on CATT_DV_071_01_______00125.ROS. This needed the closeFB to be brought forward in time by about five hours. #----------------------------------------------------------------------------# #- 4.2.2 #### Candidate 2 (NEW 2015-02-24) #----------------------------------------------------------------------------# TRAL name: TRAL_DL_006_01____P__00013 Comet activity: custom 91.4 kg/s * 980 m/s @ 1.3 AU 125 kg/s * 1000 m/s @ 1.25 AU This version differs from candidate 1 in the following points: The SPICE leap seconds kernel (LSK) was updated from naif0010.tls to naif0011.tls and the leap second on 2015-Jun-30 handled appropriately (this is before the start of LTP006, but the trajectory products do also comprise the preceding arc). Because of changed manoeuvre times by 40 minutes in LTP005 from MTP016 onwards due to a reaction wheel problem, the end point of LTP005 had slightly changed. The startpoint of LTP006 was adapted respectively. The manoeuvre times in LTP006 were also changed by 40 minutes. The pointing errors were computed neither from the HAC nor from the LAC slope, but from a custom activity slope as provided above. MTP018 was tuned to the custom activity slope. MTP019 was changed from two closeFB segments to only farFBs. Pointing error violations were not considered for MTP019. One arc of each of the two box orbits was put at 50 km and 50 deg phase angle. All arcs were made as short as possible (limited by the constraint that the velocity has to be at least two times escape velocity). MTP020 was tuned to the custom activity slope. The far excursion in MTP021 is almost unchanged. Only the box orbit onto which it returns (assumed for the beginning of LTP007) was tuned to the new activity. The latest CATT file (00144) was plugged in and the Activity Campaign closeFB in MTP018 was re-tuned to hit the Imhotep jet. A time shift of -8758 s is required. The jet is then hit at 2015-07-11T05:47:32. All files are available for three cases, distinguished by the letter directly after the ``P'' denoting the Preferred case. The three cases are: N: No phasing, manoeuvre at the nominal time of 01:40:00. M: Maximum phasing, manoeuvre 12 hours earlier at 13:40:00. _: Optimized phasing, manoeuvre 8758 seconds earlier at 23:14:02.