!  File:  2871C.PROP
!  Database:  PEPDB
!  Date:  17-FEB-1994:19:42:13

coverpage:

  title_1:         EPHEMERIS TABLE LOAD UPLINK
    sci_cat:       OPERATIONS
    proposal_for:  OV/MOC
    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.
    line_5:        Updated 1/15/91 to reflect revised MOC strategy.  Removed downlink
    line_6:        and "non-guiding" requirements.  Exposure Logsheet updates have been
    line_7:        entered directly into the PMDB.

!
! 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
    line_3:        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:        Uplink contact only needs to be scheduled.  Downlink should not be scheduled.
    line_9:        The update must be made while guiding on gyros with no need to maintain
    line_10:       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
    addr_1:        GSFC, CODE 440.8
    city:          GREENBELT
    state:         MD
    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 40 MORE
    req_2:         TIMES;
    req_3:         REQUIRES UPLINK;
    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;
    comment_1:     EPHEMERIS TABLE LOAD UPLINK.
    comment_2:     MOC PSTOL "LOADEPHM".

!
! end of exposure logsheet

! No scan data records found