From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Galileo Update - 07/24/92
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords:  Galileo, JPL
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Sat, 25 Jul 1992 02:45:07 GMT

Forwarded from Neal Ausman, Galileo Mission Director

                                   GALILEO
                       MISSION DIRECTOR STATUS REPORT
                                POST-LAUNCH
                            July 17 - 23, 1992

SPACECRAFT

1.  On July 17, realtime commands were sent to verify the commandability of
the spacecraft following the Command Processor Assembly (CPA) configuration
problem on Wednesday, July 15.  A single frame command followed by a 
multi-frame command were sent and successfully received by the spacecraft.

2.  On July 19, real-time commands, previously attempted on July 15 and
unsuccessfully received by the spacecraft, were sent to change the System Fault
Protection (SFP) to turn off the LGA-2 (Low Gain Antenna #2) motor if the
sequence memory load is terminated.  This change prevents a continuous
undervoltage situation in the low probability scenario of a relay failure
causing a DC bus short circuit while retracting the LGA-2 antenna.  The 
commands were successfully received by the spacecraft (see Special Topic 
No. 2).

3.  On July 20, the Dual Drive Actuator (DDA) pulse/Low Gain Antenna 2 (LGA-2)
stow sequence memory load was sent to the spacecraft.  The sequence was loaded
on the spacecraft without incident (see Special Topic No. 2).

4.  On July 20, realtime commands were sent to insert sun gate data into
telemetry Map 1 variable Packet No. 9.  This change will allow wobble data and
sun gate data to be obtained simultaneously during the DDA pulse/LGA-2 stow
mini-sequence (see Special Topic No. 2).

5.  On July 21, realtime 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 DDA pulse/LGA-2 stow
activities.  This change will allow the spacecraft to return to a sun-pointed
attitude if an AACS Power on Reset (POR) occurs during DDA pulse/LGA-2 stow
activities (see Special Topic No. 2).

6.  On July 21, the DDA pulse/LGA-2 stow sequence memory load went active.
The warming turn to a 31-degree off-sun attitude commenced at approximately
1757 UTC and completed at 1804 UTC.  The first of two motor turn on pulses
occurred at 1946 UTC for approximately 2 seconds, as planned.  The DDA motor
temperature was approximately minus 25 degrees C at turn on.  Initial results
indicate the motor stalled at 100 milliseconds with inconclusive evidence of
ballscrew rotation (see Special Topic No. 2).

7.  On July 22, after approximately 24 hours at the warming attitude, the
second motor turn on pulse occurred at 1801 UTC for approximately 2 seconds,
as planned.  The DDA motor temperature was approximately minus 6 degrees C at
turn on.  Initial results are that the motor stalled at 126 milliseconds
indicating some ballscrew rotation occurred.  Additionally, the spacecraft
under stored sequence control, was commanded back to a 5 degree off-sun 
attitude at approximately 18:07 UTC.  After the sun acquisition, sun gate data 
was collected to determine if an antenna rib is still obscuring the sun gate 
signal.  Data analysis indicates that the sun gate is still obscured, 
indicating no ribs released (see Special Topic No. 2).

8.  On July 23, the Low Gain Antenna (LGA-2) motors were turned on at
approximately 1946 UTC for a duration of 16 seconds to stow the LGA-2 antenna
and collect spacecraft dynamics data from the activity.  Additionally, realtime
commands were sent to perform an open loop wobble compensation.  Data analysis
is in progress.

9.  During the week, the DC bus imbalance reading has continued to change
significantly.  The DC measurement has ranged from 92DN (10.6 volts) to 151DN
(17.8 volts) and now reads 108DN (12.5 volts).  This measurement variation is
consistent with the model developed by the AC/DC special anomaly team.  The AC
measurement has remained relatively unchanged and reads 3.1 volts.

10. The Spacecraft status as of July 23, 1992, is as follows:

       a)  System Power Margin -  51 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)
       e)  Downlink telemetry rate/antenna-40 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

UPLINK GENERATION/COMMAND REVIEW AND APPROVAL:

1.  The Dual Drive Actuator (DDA) pulse/LGA-2 stow mini-sequence memory load
was approved for transmission by the Project on July 17, 1992.  This
mini-sequence covers spacecraft activities from July 21, 1992 to July 24, 1992.

2.  The EE-7 (Earth-Earth 7) final sequence and command generation package was
approved by the Project on July 23, 1992.  This sequence covers spacecraft
activities from August 10, 1992 to November 23, 1992.


TRAJECTORY

     As of noon Thursday, July 23, 1992, the Galileo Spacecraft trajectory
status was as follows:

        Distance from Earth         125,608,000 miles (1.35 AU)
        Distance from Sun           166,926,000 miles (1.80 AU)
     	Heliocentric Speed           46,300 miles per hour
     	Distance from Jupiter        670,891,000 miles
        Round Trip Light Time        22 minutes, 38 seconds


SPECIAL TOPIC

1.  As of July 23, 1992, a total of 8062 real-time commands have been
transmitted to Galileo since Launch.  Of these, 3190  were pre-planned in the
sequence design and 4872 were not.  In the past week, 28 real time commands
were transmitted; 25 were pre-planned in the sequence design and 3 were not.
In addition, 5453 mini-sequence commands have been transmitted since March 
1991; 3201 were pre-planned and 2252 were not. In the past week, 414 
mini-sequence commands were transmitted.  Major command activities this week 
included commands to verify the commandability of the spacecraft, update the 
System Fault Protection (SFP), uplink the DDA pulse/LGA-2 stow sequence memory
load, update the telemetry map variable packets, and perform wobble 
compensation.

2.  The High Gain Antenna (HGA) DDA pulse/LGA-2 stow activities are scheduled
from July 21 to July 24, 1992.  The warming turn to a 31 degree off-sun 
attitude along with the first DDA two second motor turn on was performed on 
July 21.  The spacecraft remained at the warming attitude for approximately 
24 hours.  The second DDA motor turn on was performed on July 22 just prior 
to the spacecraft turning back to a 5 degree off-sun attitude.  Sun gate data 
was collected after the sun acquisition completed.  The LGA-2 motors were 
turned on for 16 seconds on July 23 and the LGA-2 antenna was successfully 
stowed.  The star scanner checkout, along with collection of sun gate and 
wobble data is scheduled during the July 23-24 time period.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Most of the things you 
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | worry about will never
|_____|/  |_|/       |_____|/                     | happen.

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