Author Topic: LDEF retrieval/return vs. second SMM retrieval/boost?  (Read 2045 times)

Offline zubenelgenubi

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I seem to recall...

After the 1988 Discovery return to flight, and also during the Solar Cycle 22 rise to maximum in 1989, that there were plans for the STS program to retrieve 2 LEO satellites:

retrieve and return LDEF (Long Duration Exposure Facility) for study;

retrieve and boost SMM (Solar Maximum Mission).

Both satellites were in decaying orbits, and the decay rate was greater than average due to the increasing solar activity.  Both satellites were in orbits of 28.5 degrees inclination.

LDEF was retrieved by the crew of Columbia on STS-32 in January 1990, about 1 month before LDEF's predicted re-entry.  I understand its (unplanned) multi-year sampling of the LEO environment, particularly MMOD, was vital to the design of Freedom/USOS portion of ISS.

SMM re-entered Earth's atmosphere on December 2, 1989.
***

Was SMM fully functional until it lost attitude control due to upper atmospheric friction?

Was a 2nd SMM retrieval mission for Shuttle planned?  If so, what happened to the mission--was it cancelled because the program ran out of time, or available hardware, or money?

Did the situation come down to--we can save LDEF, or we can save SMM again, but we can't save both?

(The ESA/NASA SOHO satellite didn't launch until December 1995--wasn't there a solar observation "gap" between SMM and SOHO?)

Thank you in advance.
« Last Edit: 09/22/2017 07:30 PM by zubenelgenubi »
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Offline Jim

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Re: LDEF retrieval/return vs. second SMM retrieval/boost?
« Reply #1 on: 09/22/2017 07:51 PM »

1.  Was SMM fully functional until it lost attitude control due to upper atmospheric friction?

2.  Was a 2nd SMM retrieval mission for Shuttle planned?  If so, what happened to the mission--was it cancelled because the program ran out of time, or available hardware, or money?

3.  Did the situation come down to--we can save LDEF, or we can save SMM again, but we can't save both?


1.  yes

2 it was to be a science payload swap out with EUVE payload (or another I believe)

3.  SMM was still functioning, there was no reason to retrieve it.

Offline zubenelgenubi

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Re: LDEF retrieval/return vs. second SMM retrieval/boost?
« Reply #2 on: 09/22/2017 09:22 PM »

1.  Was SMM fully functional until it lost attitude control due to upper atmospheric friction?

2.  Was a 2nd SMM retrieval mission for Shuttle planned?  If so, what happened to the mission--was it cancelled because the program ran out of time, or available hardware, or money?

3.  Did the situation come down to--we can save LDEF, or we can save SMM again, but we can't save both?


1.  yes

2 it was to be a science payload swap out with EUVE payload (or another I believe)

3.  SMM was still functioning, there was no reason to retrieve it.

Re: 2.  Yes, I followed up on Gunter's web site--the satellite would be refurbished on the ground to become Extreme Ultraviolet Explorer.
(Later, EUVE would have been had its instruments swapped out on-orbit to become XTE, X-ray Timing Explorer.)
 
Re: 3.  The retrieval would have facilitated a boost to a higher orbit, such as was done on some (all?) HST retrieval missions, even if there was nothing on SMM to replace or repair.  A return to SMM's nominal orbit would allow a further mission extension.

Was this considered, even if there was nothing to repair or replace, but ultimately rejected?
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Offline Jim

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Re: LDEF retrieval/return vs. second SMM retrieval/boost?
« Reply #3 on: 09/22/2017 09:40 PM »

Re: 3.  The retrieval would have facilitated a boost to a higher orbit, such as was done on some (all?) HST retrieval missions, even if there was nothing on SMM to replace or repair.  A return to SMM's nominal orbit would allow a further mission extension.

Was this considered, even if there was nothing to repair or replace, but ultimately rejected?

After Challenger, there were there were few reasons to go to 28 degrees inclination.   The only ones were IUS deployments, HST deployment and servicing, few other deployments and LDEF retrieval.  There was little justification to fly to SMM as a solo mission, and there was nothing to share the payload bay, with the FSS structure required for reboost.
« Last Edit: 09/22/2017 09:46 PM by Jim »

Offline Jim

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Re: LDEF retrieval/return vs. second SMM retrieval/boost?
« Reply #4 on: 09/22/2017 09:50 PM »
Ignore the above.  SMM deorbited in Dec 1989.  This was even before the LDEF retrieval.  2 TDRS, 3 DOD, Magellan and Galileo flew before it reentered.  It was not a priority at the time

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