The complicated task of remotely switching the Hubble Space Telescope (HST) over to its Science Data Formatter (SDF) “Side B” of the Science Instrument Command and Data Handler (SIC&DH) has been completed with only a few minor issues – issues which became worse on Friday.
HST engineers started transmitting lines of complex programming to the aging telescope on Wednesday, which included one final attempt to bring Side A to life.
Engineers are back in contact with Side A, and are utilizing data to gain diagnostic information from the Control Unit/Science Data Formatter (CU/SDF) hardware.
Transition to Side B has been issue-free, with engineers receiving telemetry that verified they had good data. Hubble’s 486 computer was reloaded with data and successfully performed a data dump back to the ground to verify all the loads were proper.
Hubble was then brought out of safe mode and the 486 computer was placed back in control. Engineers have reconfigured Side B’s computers to execute pre-science command loads and resume communications satellite tracking with the HST high gain antennas.
It was expected to take until Friday to complete the task of swapping over to Side B. However, the process was completed in just over 20 hours.
Everything seemed to be going as hoped until Friday, when two anomalies were observed during the activation of HSTs’ science instruments, and the resumption of science observations – which have now been suspended.
The first event occurred at approximately 1:40 PM on Thursday when the Advanced Camera for Surveys (ACS) suspended operations due to indication that one power source in the Solar Blind Camera’s low voltage power supply failed to turn on.
This was the first turn on of the Solar Blind Camera since its last use prior to the safing of HST’s NASA Standard Spacecraft Computer, version 1 (NSSC-1) on September 27.
The first step taken in investigating the NSSC-1 safing was to collect a memory dump. This dump was success. The data shows that yesterday’s anomaly is likely different from the one that occurred on Sept. 27.
Initial indications point to a potential problem in the B-side of the Computer Processing Module (CPM-B). The CPM-B had not been used on orbit prior to Wednesday evening’s activation of Side B of the Science Instrument Control & Data Handling (SIC&DH) unit.
The spacecraft computer is continuing to execute command loads sent to it from the Space Telescope Operations Control Center (STOCC) at GSFC, and all of its subsystems are nominal. The investigation is continuing.
Hubble’s replacement hardware – which will hand the telescope a new Side A and Side B – is the key driver to STS-125’s launch date, which is currently tracking February 17 NET (No Earlier Than).
HST managers have noted that the hardware needs to undergo several months of pre-flight checkouts, including vibration testing, before being shipped to the Kennedy Space Center (KSC) for integration into Atlantis’ payload.
Should the timeline prove to be too restrictive on the February launch target, Discovery – on STS-119 – would return to the previously allocated widow, with Atlantis moving to April/May. This is mainly related to the need to have a LON (Launch On Need) shuttle “dual processed” for STS-125’s rescue requirements.
“Manifest Options: The Hubble Space Telescope team continues to evaluate their schedule for delivery of requalified spare hardware for launch on STS-125 to recover science operations,” noted Tuesday’s 8th Floor News (HQ memo).
“The expectation is that they will have a better understanding of their schedules in early November, which will factor into the decision on whether STS-125/HST or STS-119/15A launches in February.”
When the decision will be taken is believed to be November 5, according to STS-125 Mission Director Chuck Shaw. However, this all depends on the status of Hubble and its delivery timelines associated with the replacement hardware.
“The first pinch point in trying to protect STS-125/HST, STS-119/15A, and STS-401/OV103 HST LON all in February is flight software products, currently driving a late October decision date,” added the memo.
“However, depending on the results of the Flight Design assessment of the STS-401 template, it may be possible to delay the decision to mid-November, which syncs well with Hubble’s decision timeline.
“Bottomline is that folks are working all angles to ensure manifest decisions are made with the best data possible. So stay tuned, we’ll know more in a few weeks.”
STS-125’s payload has finally been removed from Pad 39A’s PCR (Payload Changeout Room), following a delay due to poor weather in the local area. This will free Atlantis for rollback on the 20th.
“The HST Payload canister was lowered last night and transferred to the PHSF (Payload Hazardous Servicing Facility) today,” noted processing information.
“Integrated preps for rollback are scheduled to begin today. RSS (Rotating Service Structure) move to park is scheduled for 1st shift Sunday, and 1st motion for rollback is scheduled for 0000 hours Monday.”
An issue with Atlantis is also being worked at the pad, which relates to a MDM (Multiplexer/Demultiplexer) card – the same hardware that caused a split of the GPCs (General Purpose Computers) on Discovery during pre-launch preparations ahead of STS-124.
“Documenting MDM OA2 reporting a Wrap failure. The team conducted troubleshooting again yesterday to try to isolate the condition,” added processing information. “MDM OA2 is still failed. MDM failed immediately upon power application to main busses.
“PCMMU (Pulse Code Modulation Master Unit) switched from 2 to 1 after power up. All MDM wraps are good in PCMMU 1.”
No issues have been reported with Atlantis’ GPCs – which read data and send commands to the MDMs – with the card likely to be changed-out either before rollback, or once back inside the Vehicle Assembly Building (VAB).