Hubble Trouble

Total failure of Control Unit/Science Data Formatter - side A on saturday,
no data being downlinked.
Attempt to switch to untested side B soon, which could restore functionality.

Also considering emergency repair as part of SM4, SM-4 is delayed.

The failure is in an electronics module.
The failure precludes science data communication to the ground or retrieval from onboard storage.
Module has redundant backup which is untested.
It may be necessary to do emergency replacement of the module if possible, on the next servicing mission, SM4.
SM4 is postponed while the backup module is tested and feasibility of a replacement during a spacewalk (EVA) is considered.
If the module is replaced during EVA, then likely some other planned servicing task will be lost.

NASA Telecon at 6 pm today - if you're on it, send me a note about what they said.

"The malfunctioning system is Hubble's Control Unit/Science Data Formatter - Side A. Shortly after 8 p.m. on Saturday, Sept. 27, the telescope's spacecraft computer issued commands to safe the payload computer and science instruments when errors were detected within the Science Data Formatter. An attempt to reset the formatter and obtain a dump of the payload computer's memory was unsuccessful.

Additional testing demonstrates Side A no longer supports the transfer of science data to the ground. A transition to the redundant Side B should restore full functionality to the science instruments and operations.

The transition to Side B operations is complex. It requires that five other modules used in managing data also be switched to their B-side systems. The B-sides of these modules last were activated during ground tests in the late 1980's and/or early 1990, prior to launch.
The Hubble operations team has begun work on the Side B transition and believes it will be ready to reconfigure Hubble later this week. The transition will happen after the team completes a readiness review.

Hubble could return to science operations in the immediate future if the reconfiguration is successful. Even so, the agency is investigating the possibility of flying a back-up replacement system, which could be installed during the servicing mission. "

The Control Unit/Science Data Formatter interfaces with the Data Management Unit which actually communicates with the science instruments.

"The heart of the SI C&DH unit is the CU/SDF. It formats and sends all commands and data to designated destinations such as the DMU of the SSM, the NASA computer, and the science instruments. The unit has a microprocessor for control and formatting functions.

The CU/SDF receives ground commands, data requests, science and engineering data, and system signals. Two examples of system signals are "time tags," clock signals that synchronize the entire spacecraft, and "processor interface tables," or communications codes. The CU/SDF transmits commands and requests after formatting them so that the specific destination unit can read. For example, ground commands and SSM commands are transmitted with different formats. Ground commands use 27-bit words, and SSM commands use 16-bit words. The formatter translates each command signal into a common format. The CU/SDF also reformats and sends engineering and science data. Onboard analysis of the data is an NSSC-I function."

It is dual redundant, but the spare side has never been used. We'll see how it is after all these years.
Hubble will not work without it.
If side B does not power up, the fourth servicing mission is pointless, so NASA has to put it on hold and decide whether to add CU/SDF replacement as a priority task.
The module it is part of is configured for EVA access and has, I believe, been tinkered with on past servicing missions.

I do not know if there are spare CU/SDFs lying around...

EVA access of Power Control Unit, on same electronic module as the CU/SDF, on a previous servicing mission (from Sky & Telescope)

F#ck!
What a day.
Anyone have any good news?