From PPS: At a meeting of the FOT and power engineers, the battery anomaly was discussed. Because of the load shedding made possible by turning off VIRS, battery 1 is fully recovered. Both battery 1 and battery 2 are charging nominally. Battery 2 is running at a higher temperature than before. There was still some concern expressed that if VIRS was turned on, then during certain orbits and certain beta angles, the charging anomaly might reoccur.
Discussion followed concerning the effect of potentially having to turn VIRS on and off (as a load shedding approach during certain times) on remaining battery life. With a 16 plus year old battery, this now may become the limiting factor on a longer TRMM mission.
Since the prime science goal is to keep the 2 prime instruments (TMI and PR) working as long as possible, the key goal seems to be to lessen the load on the battery. So we need to minimize the possibilities of further anomalies, lower the battery charging load, and generally decrease demand on the batteries. As a result, the science team made the decision at this time to keep VIRS turned off.
We would be interested in hearing from users what the impact this has on you and your research. Also, we would welcome TRMM science user's input as to the effect of this VIRS outage on their work vs. the desirability of extending operation of TMI and PR.
We do want our users to know there is no absolute analytical way to determine the remaining life in the batteries. Also, there is no analytical way to establish how much additional life would be added by the battery load reduction but there was general consensus among the experts that it would increase the life of the battery.
The Flight Operations Team and power specialists will continue to monitor the battery.
The power team is also going to look at life cycle testing done during TRMM development to see what, if anything that might add to the understanding of the on-board battery remaining capacity.
Accordingly, the TRMM science team has made the decision that for the time being, the VIRS instrument will remain off.
IMPORTANT MESSAGE Mar 26, 2014 Update on VIRS and battery anomaly
From PPS: The battery situation aboard TRMM has stablized with the loadshedding.
Currently both batteries are in a nominal state. The FOT is studying other possible ongoing load shedding activities short of turning off an instrument. They are also studying the proper procedures for turning on VIRS (this hasn't been done since 2001).
The current plans call for VIRS to be turned on sometime next week. The batteries will then be monitored to see if charging remains nominal. Should charging anonmalies appear again, it will be necessary to shutdown VIRS again.
IMPORTANT MESSAGE Mar 24, 2014 Important: VIRS has been turned off for the time being
From PPS: Due to a battery charging anomaly on TRMM, VIRS has been turned off (3/21
17:02 UTC) as part of a load shedding approach for dealing with the
This approach seems to be working well as battery charging is returning to
TMI, PR and LIS remain on and continue to provide NRT data.
Note will be sent out when the situation changes.