From: Mike Machado [Michael.J.Machado.1@gsfc.nasa.gov]
Sent: Tuesday, May 08, 2007 4:27 PM
Subject: Polar instrument power related requests

Importance: High

Instrument teams,

Due to the Polar Power conditions we are experiencing, the FOT has also 
observed battery discharging during supports and charging between contacts. 
This is making the battery temperatures drop below their red limits (-5 deg 
C).  The battery temperature trend is slowly continuing downward. This may 
slightly affect battery performance but should only be a temporary impact 
(until temperatures reach below minus 20 deg C at which point there may be 
irreparable damage).

Reducing the bus load should alleviate this situation. To help in this 
matter, the FOT has begun reducing the contact times that do not impact 
data recovery (i.e. changing those 2 hours supports targeted for instrument 
commanding to 1 hour) in order to improve the battery recharge cycle. 
Trending data indicates that Polar is closer to power negative conditions 
than we would like to be. As we continue to observe Polar and analyze the 
plots, here are some requests the FOT has for the instrument teams.

Please let us know:
If you have a pre-canned sequence of shutdown commands that can be executed 
safely without prior notification.
If you have any thermal concerns (temps reaching below limits with 
instrument on or off).
If you have any heaters or other loads that are regulated automatically 
(what are they and what is the power draw?).

As always, we would prefer to perform instrument power downs in a gradually 
planned manner, but may not have the luxury. If an extremely low 
temperature can impact the instrument health and safety, or if loads could 
be automatically added to the bus, it will impact the operational response.

Thanks,

Mike


==========================================================================
Michael J. Machado
WIND/POLAR Flight Operations Team Manager
Phone: +1 301 286-0666
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