! File: 2911C.PROP ! Database: PEPDB ! Date: 17-FEB-1994:21:10:57 coverpage: title_1: EPHEMERIS TABLE LOAD UPLINK sci_cat: OPERATIONS proposal_for: SV/MSC longterm: 15 pi_fname: ART pi_lname: BRADLEY pi_inst: HSTP-G pi_country: USA hours_pri: 0.25 realtime: X ! end of coverpage abstract: line_1: Periodic S-band single access (SSA) forward link service to the S/C is desired line_2: for updating the vehicle ephemeris coordinates. ! ! end of abstract general_form_proposers: lname: BRADLEY fname: ART inst: STP-G country: USA ! ! end of general_form_proposers block general_form_text: question: 2 section: 0 line_1: The ephemeris clock in the DF-224 flight computer rolls over every 11.5 days. line_2: Furthermore the accuracy of the ephemeris fit degrades in time, which will line_3: impact the S/C pointing. ! question: 3 section: 0 line_1: S-band single access (SSA) forward link service to the S/C will be scheduled line_2: every two days. A contact time of 10 minutes should be sufficient to load and line_3: dump the vehicle ephemeris coefficients before enabling their usage in the line_4: flight computer. One back-up contact time should also be scheduled in case the line_5: primary contact time is unavailable. line_7: The required contact time must be after a guide star acquisition termination line_8: and before the next guide star acquisition. Loading the ephemeris coefficients line_9: during this interval will ensure that the planned guide star reacquisitions and line_10: acquisitions will not be distrubed. line_12: The update cannot be done while actively guiding using the FGSs or FHSTs. It line_13: cannot be done while in gyro mode but waiting for a re-acquisition because it line_14: can affect the parallax computations. line_16: The update must be made while guiding on gyros with no need to maintain line_17: accurate attitude reference. ! question: 3 section: 1 line_1: The SMS COMCON request should contain an appropriate text message which line_2: indicates the COMCON is for loading vehicle ephemeris coefficients via the line_3: PSTOL PROC LOADEPHM. line_5: The GSFC Flight Dynamics Facility will provide predicted ephemeris data to PASS line_6: which will fit a set of coefficients to the data and establish a PORTS line_7: accessible table. The Mission Operations Contractor will execute the PORTS line_8: PSTOL LOADEPHM to load the coefficients into the DF-224 flight computer. ! question: 5 section: 0 line_1: A 10 minute contact time with the S/C should be sufficient to load and dump the line_2: coefficients before enabling their usage in the DF-224 flight computer. line_4: Loading new ephemeris coefficients at 2-day intervals should keep the in-track line_5: and cross-track errors within 60km. If the new ephemeris coefficients result line_6: in an error which exceeds 120km, then the vehicle would have to be line_7: reconfigured, which would impact science operations. line_9: Changes in ephemeris coefficients which result in changes greater than 120km line_10: requires HST to be in a flight software "drift mode" which will substantially line_11: impact routine operations ! question: 6 section: 0 line_1: Real time contacts will be required. The communications contact will be defined line_2: in the SMS as (U) for uplink and the requested rate is 1kbit. ! !end of general form text general_form_address: lname: BRADLEY fname: ART category: PI inst: HSTP-G country: USA ! ! end of general_form_address records ! No fixed target records found ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: REPEAT 1-2 EVERY 48H +/- 12H FOR 25 MORE req_2: TIMES; COND IF A / 1-2; req_3: REQUIRES UPLINK; req_4: RT ANALYSIS; req_5: CYCLE 0/ 1-6; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! linenum: 2.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: AFTER 1 BY 4H +/- 3H; req_3: REQUIRES UPLINK; req_4: RT ANALYSIS; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! linenum: 3.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: REPEAT 3-4 EVERY 48H +/- 12H req_2: FOR 25 MORE TIMES; COND IF B / 3-4; req_4: RT ANALYSIS; req_5: REQUIRES UPLINK; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! linenum: 4.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: AFTER 3 BY 4H +/- 3H; req_3: REQUIRES UPLINK; req_4: RT ANALYSIS; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! linenum: 5.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: REPEAT 5-6 EVERY 48H +/- 12H req_2: FOR 25 MORE TIMES; req_3: REQUIRES UPLINK; req_4: RT ANALYSIS; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! linenum: 6.000 targname: DARK config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: 10M priority: 1 param_1: CONTROL=GYRO, req_1: AFTER 5 BY 4H +/- 3H; req_3: REQUIRES UPLINK; req_4: RT ANALYSIS; comment_1: EPHEMERIS TABLE LOAD UPLINK. comment_2: MOC PSTOL "LOADEPHM". ! ! end of exposure logsheet ! No scan data records found