Lunar Reconnaissance Orbiter Mission Operations Review (MOR ...

LRO Open Risks
LRO Risk: LOLA Laser Design Lifetime not Qualified by Lifetest Prior to Launch Risk ID: LOLA-261*
Rank Risk Statement Approach & Plan Comments/Status
1 Given The failure in the LOLA EM
laser life test,
Then: LOLA may not achieve the
recommended 800 million shots
necessary to meet its Level 1
science requirements.
M
Mitigate:
Examine and review why EM laser lifetest
failed. Most likely cause established
(failure of laser optics common to both
lasers, possibly contamination induced).
Laser 2 cavity undamaged. Rebuild
common optics train and resume lifetest on
Laser 2 only (complete, lifetest resumed
9/19). In parallel, LRO to examine ways to
extend flight laser lifetime operationally
and plan to minimize the number of shots
at the orbiter level pre-launch. Examples:
automated safing to shut laser down if
thermistor failure causes diode
temperature increase.
Additional Watch Plan: Monitor
performance of rebuilt EM laser after
resumption of testing. Make operational
decisions based on performance during
test.
Contingency:
Assuming Laser performance floor of 500
million shots, LOLA science team to
examine impact of more-limited lifetime on
the LOLA L1 data products.
In Progress:
Apr 08: Root cause not established, effects (common optics
damage, L1 diode heat sink burn marks) known. Possible ways to
extend flight operational lifetime include safing, minimizing shots
on ground & duty cycling lasers .
May 08: As result of 5/31 LRO/LOLA risk assessment meeting,
LRO and Proj. agree that LRO proposes to fly LOLA as-is, and
will resume the EM laser lifetest ASAP, ensuring that the
hardware is as flight-like as possible .
Aug 08: Rebuild/retest of the EM laser currently on schedule to
resume extended ops testing by end of Sept.
Sept 08: Rebuild of the EM laser completed and extended vac
testing has resumed. W/launch delay, there is time for the rebuild
EM laser to reach 500 million shots by launch. Test results and
risk assessment to be monitored monthly.
Oct 08: As of 11/05, LOLA has accumulated 92 million shots in
vacuum towards the goal of 500 million shots by 4/24/09. Laser
performance is nominal.
As of 12/01, LOLA EM laser has accumulated 152 Mshots in
vacuum. Performance remains nominal (this includes normal
increasing of the switch out time, which has increased from 170
usec to 180 usec over the test to date).
Dec 08: 219 Mshot in vac as of 12/24, switch out time still 180
usec. Reassess likelihood when total number of shots hits 350-
400 million shots, predicted by the end of March.
Jan 09: As of 1/29, EM laser now at 304 million shots. All
performance, including switch out time, remains nominal.
Feb 09: As of 2/25, EM laser now at 366 million shots. All
performance parameters remain nominal. Switchout time
continuing slow, steady increase, but no changes to diode current
setting have been performed to date.
NASA’s Goddard Space Flight Center LRO Flight Operations Review (FOR) Day 1 - 38