From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Galileo Update - 10/15/92 
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords:  Galileo, JPL
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Fri, 16 Oct 1992 08:29:43 GMT

Forwarded from Neal Ausman, Galileo Mission Director

                                  GALILEO
                      MISSION DIRECTOR STATUS REPORT
                                POST-LAUNCH
                           October 9 - 15, 1992

SPACECRAFT

1.  On October 9, the Energetic Particle Detector (EPD) motor maintenance
exercise was performed which stepped the motor through its eight operating
positions and then returned it to Sector O which is the predicted least
contamination position in preparation for the execution of TCM-15 (Trajectory
Correction Maneuver #15). The motor maintenance exercise was successfully
verified by Memory Readout (MRO) commands.  Additionally, the EPD was returned
to Sector 4 at the completion of the maneuver.

2.  On October 9, the Trajectory Correction Maneuver (TCM-15) was performed
on the spacecraft.  The maneuver used the spacecraft's axial (z) thrusters and
lateral thrusters to impart a predicted total delta velocity of 0.72 m/s.
This maneuver was executed at 1200 bps with the spacecraft pointed
approximately 16 degrees off the Earth.

     The spacecraft's performance throughout the activity was normal.  All
RPM (Retro-Propulsion Module) pressures and temperatures and attitude control
indicators were near predicted levels.  After the axial and lateral burn
segments, the sequence planned spin corrections and pointing corrections were
not needed.

     Preliminary radio tracking data indicates a 0.5 percent overburn for the
axial segment and a 1.2 percent overburn for the lateral segment.

3.  On October 10, the Dual Drive Actuator (DDA-4) memory sequence load was
uplinked to the spacecraft without incident. This sequence load covers
spacecraft activities from October 12 to October 16 (see Special Topic No. 2).

4.  On October 10, Delayed Action Commands (DACs) were sent to the spacecraft
to switch from 40 bps uncoded telemetry to 1200 bps coded telemetry on
October 12 just prior to initiation of the DDA-4 sequence memory load.

5.  On October 12, real-time commands were sent to change the System Fault
Protection (SFP) AACS-INIT (Attitude and Articulation Control Subsystem)
pointing slot from the Earth to the Sun prior to the Dual Drive Actuator
(DDA-4) pulse activities.  This change will allow the spacecraft to return to
a sun-pointed attitude if an AACS Power on Reset (POR) occurs during the
DDA-4 pulse activities (see Special Topic No. 2).

6.  On October 12, cruise science Memory Readouts (MROs) were performed for
the Extreme Ultraviolet Spectrometer (EUV).  Preliminary analysis indicates
the data was received properly.

7.  On October 12, the DDA-4 memory sequence load went active.  The warming
turn to a 45-degree off-sun attitude started at approximately 2313 UTC and
completed 28 minutes later at 2341 UTC (see Special Topic No. 2).

8.  On October 14, Delayed Action Commands (DACs) were sent to turn off the
Plasma Detector supplemental heater after the sun acquisition to eliminate a
30-degree thermal cycle on the instrument.

9.  On October 14, after approximately 46 hours at the warming attitude, real
time commands were sent to enable the High Gain Antenna (HGA) Dual Drive
Actuator (DDA) motor primary relays, pulse the motors 10 times with an on time
of 0.267 seconds followed by an off time of 0.534 seconds, and then safe the
primary relays and reset the command loss timer.  The DDA motor temperature
was approximately plus 23.5 degrees C at turn on.  DDA motor current data
analysis is in progress.  Preliminary analysis indicates the motor current
during the 10 pulses was less than the stall current of 970 milliamps,
indicating some ballscrew rotation took place.

    Additionally, the spacecraft under stored sequence control was commanded
back to a 5 degree off-sun attitude at approximately 2345 UTC.  After the sun
acquisition, sun gate data was collected to determine if an antenna rib is
still obscuring the sun gate signal.  Preliminary data analysis indicates that
the sun gate field of view is still obscured, indicating no ribs released;
analysis is continuing.  Also, preliminary doppler tracking data collaborates
the sun gate data results.

10. On October 15, as part of the Dual Drive Actuator (DDA) No. 4 pulse
activities, real-time commands were sent to checkout the star scanner.  This
activity was performed as a precaution to protect the star scanner from
"seeing" bright particles which could release if an HGA rib released
(see Special Topic No. 2).

11. The AC/DC bus imbalance measurements exhibited some change. The AC
measurement has ranged from 12DN to 18DN and now reads 18 DN (4.1 volts).
The DC measurement has ranged from 117 DN (13.6 volts) to 141 DN (16.6 volts)
and now reads 129 DN (15.1 volts).  These measurement variations are
consistent with the model developed by the AC/DC special anomaly team.

12. The Spacecraft status as of October 15, 1992, is as follows:

       a)  System Power Margin -  56 watts
       b)  Spin Configuration - Dual-Spin
       c)  Spin Rate/Sensor - 3.15 rpm/Acquisition Sensor
       d)  Spacecraft Attitude is approximately 5 degrees
           off-sun (leading) and 19 degrees off-earth (lagging)
       e)  Downlink telemetry rate/antenna-1200 bps (coded)/LGA-1
       f)  General Thermal Control - all temperatures within
           acceptable range
       g)  RPM Tank Pressures - all within acceptable range
       h)  Orbiter Science- UVS, EUV, DDS, MAG, EPD, and HIC are
           powered on
       i)  Probe/RRH - powered off, temperatures within
           acceptable range
       j)  CMD Loss Timer Setting - 264 hours
           Time To Initiation - 263 hours

GDS (Ground Data Systems):

1.  Galileo Earth 2 Ground Data System (GDS) testing was conducted on October 6
and October 13, 1992 with the Galileo D1.0 ground system utilizing the MCCC
(Mission Control and Computer Center) real-time systems and the DSN (Deep Space
Network) Canberra Signal Processing Center (SPC 40).  Test objectives were to
validate the successful integration of the Galileo D1.0 ground system with the
DSN and MCCC system that will be used to support the Earth 2 activities.
Real-time analysis indicated all objectives were successfully met, however
some post-test analysis of data is on-going in the MTS and PFOE areas.

TRAJECTORY

     As of noon Thursday, October 15, 1992, the Galileo Spacecraft trajectory
status was as follows:

	Distance from Earth         31,353,400 miles (.34 AU)
	Distance from Sun           121,071,200 miles (1.30 AU)
	Heliocentric Speed           63,400 miles per hour
	Distance from Jupiter        611,760,500 miles
	Round Trip Light Time        5 minutes, 42 seconds


SPECIAL TOPIC

1.  As of October 15, 1992, a total of 8324 real-time commands have been
transmitted to Galileo since Launch.  Of these, 3367 were initiated in the
sequence design process and 4957 initiated in the real-time command process.
In the past week, 87 real time commands were transmitted: 79 were initiated
in the sequence design process and 8 initiated in the real time command
process.  In addition, 5911 mini-sequence commands have been transmitted
since March 1991; 3753 were pre-planned and 2158 were not.  In the past week,
234 mini-sequence commands were transmitted.  Major command activities this
week included commands to reconfigure the telemetry rate, update system fault
protection parameters, turn off the PLS supplemental heater, pulse the DDA
motors, and checkout the star scanner.

2.  The Dual Drive Actuator (DDA) pulse mini-sequence No. 4 covers spacecraft
activities from October 12 to October 16.  The warming turn to a 45-degree
off-sun attitude occurred on October 12.  The spacecraft remained at the
warming attitude for approximately 48 hours.  The DDA 10-pulse hammer test
occurred after approximately 46 hours at the warming attitude.  The sun
acquisition back to approximately a 5 degree off-sun attitude occurred on
October 14.  Sun Gate data was collected on October 15.  The star scanner
checkout along with the collection of wobble data is scheduled for October 16.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | If God had wanted us to 
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | have elections, he would of 
|_____|/  |_|/       |_____|/                     | given us candidates.