Wednesday, March 1, 2000 (DOY 054/19:00:00 to DOY 061/19:00:00 UTC)

Launch / Days since Launch = Nov 7, 1996 / 1213 days

Start of Mapping / Days since Start of Mapping = April 1, 1999 / 335 days
Total Mapping Orbits = 4390

Total Orbits = 6072

Recent Events:

The spacecraft continues to operate nominally in performing the daily recording and transmission of the science data. The
mm016 sequence executed successfully from 00-55 (2/24/00) through 00-58 (2/27/00). The mm017 sequence began
execution on 00-59 (2/28/00) and will run through completion of 00-61 (3/1/00). The next sequence mm018, scheduled to
execute from 00-62 (3/2/00) through 00-64 (3/4/00), has been successfully uplinked to the spacecraft.

The first fixed-HGA sequence of the beta supplement mapping phase, mm019, has been generated and will be uplinked
Saturday March 4. The mm019 sequence will begin execution on 00-65 and continue through 00-68 (3/8/00). Included in
the mm019 sequence is the first of the monthly off-nadir polar scans for the MOLA instrument, approved by the Program.
The first 12 orbits of the mm019 sequence will fly with a -17.1 degree nadir off-point angle for 45 minutes centered about
the South Pole and a 14.4 degree nadir off-point angle for 45 minutes centered about the North Pole. For the fixed-HGA
mapping operations, the spacecraft will be nadir pointed for 24 hours, recording science data on the solid state recorders,
then the spacecraft will be oriented to point the HGA bore-sight at Earth for an eight hour playback period to return the
data collected on the recorders. During this eight-hour period, the spacecraft will not be nadir pointed and not collecting
science data, with the exception of radio science which will perform atmospheric observations as the spacecraft enters
and exits Earth occultation. As reported last week the reason for the fixed-HGA sequences is to provide radio science
atmospheric observations near the South Pole as the spacecraft exits Earth occultation, a geometry not supported by the
HGA gimbals in the beta supplement operations due to EMI and HGA boom interference constraints. Upon completion of the
data playback at the end of the eight-hour Earth pointed period, the spacecraft will be turned back to nadir pointing to
begin the next fixed-HG A cycle

Spacecraft Health:

All subsystems are reporting nominal health. Three more PDS reset occurred over the last week. The frequency has been
increasing over the last two weeks. So far no cause has been found for the recurring resets. The resets appear to have
minimal if any impacts to the instruments. We continue to forward all reset data to the PDS software experts at JPL.


There have been 21 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files,
instrument command loads, and the mm017 and mm018 sequences. Total command files radiated to the spacecraft since
launch is 4480.

Upcoming Events:

The Navigation team has been looking at the ground track walk on a weekly basis to determine if an orbit trim maneuver
(OTM) is required. Prior to the start of beta supplement operations, it appeared that an OTM would be needed sometime
in March. However, the latest tracking data for the first few weeks of beta supplement operations shows the rate of the
ground track walk decreasing and starting to knee over, which if the trend continues will not necessitate an OTM in the
near term. With the likelihood of the next OTM diminishing, planning has begun for a focus calibration of the MOC to be
performed in the next few weeks.