The USGS is pleased to announce that Landsat 5 resumed imaging on January 10, 2008. Landsat 5 imaging was suspended on October 6, 2007 due to a battery cell failure with one of its two working batteries. The Flight Operation Team determined that 1 of 22 cells failed in one of the batteries. This reduces the overall power available from the batteries and requires a new battery charging procedure to avoid overheating.
In November 2005, Landsat 5 transitioned to operations using a fixed solar array due to a failed motor which reduces the efficiency of battery charging. This, combined with the reduced power available from the batteries, increases the complexity of maintaining a safe power balance while collecting imagery.
Over the next few weeks, the team will continue to increase collection of imagery while closely monitoring power. Data collected will be available soon following analysis and calibration of the data.
Landsat 5 remains stable. However, Thematic Mapper imaging is still suspended. Battery #2 has been brought back online for characterization and testing, which is expected to take several weeks. The Flight Operations Team will recommend options for continued operations at that time. Further updates will continue to be posted as information becomes available.
Battery-2 was brought on-line by the L5 FOT on 19 November, at approximately
18:00z, successfully completing phase-1 of the current recovery effort. The
overall performance of the Power Subsystem has been nominal and very stable
for the past 48-hours; with Battery-2's performance exceeding expectations,
once again.
As the FOT continues to closely monitor S/C power, engineers are preparing
procedures to configure the payload for a return to full-time imaging operations.
The timeline for instrument turn-on and initial imaging sessions remains
on the order of weeks.
L5 would like to take this opportunity to thank everyone for their understanding
and support during the past 6-weeks. We will continue to keep you apprised
of our status as changes occur.
Landsat-5 imaging operations were put on hold due to a Battery-2 anomaly
that occurred on DOY-279 (5 October). Ever since that time, engineers have
been analyzing telemetry and working on a recovery plan to put Battery-2
back on-line and eventually resume normal imaging operations.
Following weeks of successful preliminary VT testing with Battery-3, and
numerous planning and review sessions, the Landsat-5 FOT performed a series
of tests on 8 and 9 November that put Battery-2 back online for the first
time since DOY 279. The sequence of Battery-2 tests concluded nominally,
as Battery-2’s performance exceeded all expectations during an entire orbit
while operating online. Battery-2 is currently back offline, with L5 returning
to minimum power configuration for the weekend.
Current plans (open to further analysis and consideration) have Battery-2
going online for full time operations by the middle of next week. The timeline
for instrument turn-on and initial imaging sessions is presently on the order
of weeks.
We will continue to keep you apprised of our status as changes occur.
Landsat 5 has been collecting global data sets continuously since it was launched in March 1984. The satellite has had a series of anomalies and has lost redundancy in onboard systems, but continues to collect high-quality data.
Early Saturday, October 6, 2007, the Landsat 5 Flight Operations Team (FOT) noted that battery #2 was automatically taken off-line the previous evening. All imaging was stopped in order to conserve power. Landsat 5 has three 22-cell Nickel Cadmium batteries. During the non-sunlit part of each orbit, the batteries provide power to sustain the satellite's electrical needs. During the day-lit period of the orbit, the solar array re-charges the batteries and meets the electrical demands of the satellite. Previously, on May 21, 2004, Landsat 5's battery #1 was taken offline following an anomaly. With the loss of battery #2, Landsat 5's remaining battery may have sufficient capacity to maintain the health and safety of the spacecraft and potentially continue with some level of day-lit imaging operations. Although the mission can operate with only 1 healthy battery, the potential loss of battery #2 would mean a loss in the level of redundancy.
The satellite continues to operate on battery #3, but is not collecting imagery. In this configuration, battery #3 appears to be operating normally and maintaining an adequate charge to operate the mission to required health and safety standards. Also, the FOT has uplinked a new command load that ensures health and safety of the spacecraft operating with only one battery. It is expected that the spacecraft can operate indefinitely in this configuration (barring any further complications).
Three phases to the investigation and recovery activity are underway. Each successive phase will be dependent on the outcome of the previous phase. The tentative plan includes:
Phase 1 - Maintain and ensure the continued operation of Landsat 5 utilizing only battery #3.
Phase 2 - Determine the optimum charging profile with battery #2 and battery #3 on-line. Bring battery # 2 back on-line and monitor performance. If battery #2 and battery #3 can be charged to produce sufficient power, there is a potential to operate in this configuration.
Phase 3 - Investigate bringing battery #1 back into service.
Over the last 3 weeks the FOT, with additional battery expertise from industry, has been working through these phases. The team is currently working on Phase 2 of the plan and will work with battery experts in mid-November to bring battery #2 back on-line. By the end of November, the team will have sufficient information to make a recommendation on the Landsat 5 mission concept - return to full operations or a more limited operations concept.