From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Ulysses Update - 09/01/92
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords:  Ulysses, JPL, ESA
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Thu, 3 Sep 1992 01:27:32 GMT

Forwarded from Peter Beech, Ulysses Mission Operations Manager

SUBJECT:  ULYSSES MISSION OPERATIONS REPORT No. 106

PERIOD: 25th to 31st August 1992


1. MISSION OPERATIONS

     Experiment reconfigurations have been carried out as
     required.

     On 26th August a HED (Magnetic Field instrument) calibration
     was carried out.

     Further BAM-I (Solar Wind Plasma) counter overflows have been
     observed during the reporting period.  The cause is still under
     investigation by the instrument team.  Anomaly Report No.
     26 has been raised to cover this anomaly.

     Also in the STO (Radio and Plasma Waves) experiment, parameter
     error flags have been giving non-zero values on a regular basis.
     The instrument team are analysing the significance of these
     events.  Anomaly Report No. 27 has been raised to cover
     this anomaly.

     The spacecraft achieved maximum range from the Earth on
     26th August.  The range on this date was 938,488,610 Km.

     Routine Earth pointing manoeuvres were performed on 26th
     and 29th August.

     On 30th August Antenna problems at Canberra caused 45
     minutes of real time data and 90 minutes of playback data
     to be lost.

     On 31st August bad weather at the Madrid complex caused
     16 minutes of real time data and 32 minutes of playback
     data to be lost.

     An average of 96.97 % data recovery was achieved during
     the reporting period.

     The percentage of data acquired as a function of bit rate
     is as follows:

     1024 bps 54.32 %
      512 bps 42.39 %

     A reduction in the number of ranging passes continued
     during the reporting period in order to improve the poor
     signal to noise ratio encountered at the present large
     spacecraft-Earth distances.



2.  SPACECRAFT STATUS

     POWER

     Nominal.
     Estimated S/C power consumption 259 watts.

     AOCS

     Nominal.

     TTC

     The spacecraft is currently configured with receiver 2 as
     the prime unit fed via the high gain antenna and with
     receiver 1 as backup fed through the low gain antenna
     (LGA-F). The downlink is provided through EPC2/TWTA2.

     The 34 meter ground stations are in use to support TTC
     operations, with at least one 70m station pass per week
     to support ranging.

     Received downlink level -148 dBm.(34 meter) X-band.

     (Variations of up to 10 db. can be expected as a result
     of station antenna in use, local weather conditions, and
     spacecraft antenna off-pointing).

     Received uplink level -127 dBm.


     DATA HANDLING

     The anomaly on CTU2 (Central Terminal Unit) reported in
     previous Operations Reports is still under investigation.
     However, some conclusions have now been reached which point
     to an electrical connection between two adjacent data lines
     as a result of component failure.  The operational impact of
     this anomaly is being studied by both the Spacecraft
     Control Team and the instrument teams in the event that
     this CTU would have to be configured for operational use.

     THERMAL

     Nominal.


3.   FLIGHT DYNAMICS

     Solar Aspect   The angle decreased from 1.97 on
     Angle (deg.)   25th August to 1.52 on 31st August.

     Sun-Probe-Earth  The angle decreased from 1.88 on
     Angle (deg.)     25th August to 1.50 on 31st August.

     Spin Rate               4.982 rpm.



4.   ORBITAL DATA

     Data taken at 13:00 PDT on 31st August.
     Distance from Earth                937,998,473 km.
     Velocity relative to the Earth         115,521 km/hr.
     Velocity relative to the Sun            31,028 km/hr.
     Ecliptic latitude                          9.1 deg/south



5.   PLANNED OPERATIONS

     Routine data gathering operations will continue together
     with experiment reconfigurations as required.

     On 1st September the Sun-Earth-Probe angle (SEP) will be
     at a minimum.  Since Ulysses is now 9.1 degrees south of
     the Ecliptic Plane this geometry will not give rise to a
     Conjunction and no special operations will be necessary
     for Sun avoidance as they were in August 1991.

     Earth pointing manoeuvres will be performed on 1st, 3rd
     and 7th September.

     Periods of 2048 bps at low antenna elevations will be
     avoided to improve the signal to noise ratio in the
     coming months.  This will slightly reduce the percentage
     of 1024 bps real-time data received.  During this period,
     70m passes will also be scheduled to perform ranging at
     large spacecraft-Earth distances while maintaining the
     desired bit rates.


6.  GROUND SEGMENT

     The ground segment performed nominally during the
     reporting period with the exception of the two incidents
     reported above.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Anything is impossible if
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | you don't attempt it.
|_____|/  |_|/       |_____|/                     | 

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