ISS MER Management’s Daily Notes Friday, June 15, 2001 – 12:00 pm,
The following notes highlight the ISS activities within the last 24 hours that were discussed during the morning NASA and Boeing management teleconferences, as well as the daily MER Management & Subsystem Tag-Up. These notes are not intended to provide the current configuration of the ISS systems, nor are they intended to capture all of the events that have occurred in the past 24-hour period or that are planned for the next 24-48-hour period. For a detailed overview of the last 24-hour period and upcoming ISS events, refer to the “0800 Report” and “Daily Report”, published by MOD on its Mission Control Center (MCC) website at http://mod.jsc.nasa.gov/mcc (select “Realtime Mission,” then “ISS Msgs”).
4B Solar Array Testing: The 4B solar array was placed in rate mode yesterday morning. Since that time, the motor current has remained steady between approximately 0.3-0.5 amps, with no sustained high-current events occurring (high current event is 0.5-amp or greater for 10-minutes or longer). The MOD and MER teams will continue to watch the motor current and, should a high-current event occur, execute the agreed-upon procedures in the test plan to try and further isolate why the high-current events have been occurring.
Service Module Batteries: R&R activities to swap the batteries in SM battery positions 2 and 6 were completed. The battery placed into the #6 slot remains off since that battery and the #6 PTAB were failed. Charging of the battery placed in the #2 slot was initiated.
SSRMS: SSRMS operations on the redundant string were performed yesterday with no recurrence of the ACU/JEU transmit/receive errors. Airlock grapple, unberth, and install dry run trajectories were run without any problems. A few problems were encountered during the operations, however. (1) During grapple fixture release, the SSRMS hung up, and then released with motion and contacted the grapple fixture. The working theory for this event is that residual stresses in the arm from the previous grapple, compounded by a possible slight thermal deformation on the vehicle (between the Lab PDGF and PMA-2 Port FRGF) from the recent XPOP-to-XVV transition contributed to this event. Investigation is ongoing, but a potential procedural change may be to “limp” the arm prior to removal from the grapple fixture. (2) An Elbow Pitch Motor RDC message went in and out of alarm once during ungrapple activities. The message/BIT was cleared and remained cleared. Motor currents higher than expected were observed for a short period of time while the SSRMS was being removed from the grapple fixture, so preliminary indications are that the hang-up of the LEE on the grapple fixture may have contributed to the RDC message. The RDC message has occurred previously and is being investigated under an existing CHIT. (3) Several video routing problems occurred during the initial operations, primarily because of set up / execution problems. These problems are already covered by existing PRs. (4) The joint selector was inadvertently switched to SPDM, which safe’d the SSRMS since no SPDM is present on-orbit. The switch was reset and operations were immediately recovered.
After completing the operational dry-run, the SSRM was maneuvered to give a view of the tip LEE from the elbow tip camera instead of grappling the Lab. This was done to inspect the LEE to see if any damage occurred while removing the LEE from the grapple fixture, or whether there was any debris or other identifiable problem that would have caused hang-up while the SSRMS was being removed from the PDGF. The SSRMS will be left in its current position (with the LEE pointing at an angle of 73 degrees from the velocity vector) until Saturday, when additional operations with the SSRMS will resume. Software Patch #3 was reinstalled in case the ACU/JEU transmit error recurs over the next day to enable diagnostic testing to be performed. The patch will be removed again prior to Saturday’s operations.
EAS and Spare SASA Connectivity Issue: The ART met this morning at 8:00am to compile its list of options for resolving the Spare SASA and Prime SASA RT Addressing conflict. As noted previously, the prime SASA and spare SASA have the same RT address, so if the spare SASA is powered up, a bus conflict will occur, resulting in a loss of communications and potentially a bus failure. The potential for this to occur on-orbit currently exists, but it has not occurred since the spare SASA has not been powered up. The spare SASA would only be powered up if the heater string failed and operational power was needed to maintain the spare SASA above minimum thermal limits. A flight rule is being established to prohibit powering up the spare SASA for the current stage and 7A. When the EAS is installed on 7A.1, a Y-Jumper to be installed that will allow the EAS and spare SASA to share the same power and data lines would automatically power up the spare SASA, causing the RT address conflict to occur.
The potential resolutions identified for resolving the issue are: (1) Remove pins from connectors on the jumpers to fly on 7A.1 to terminate the in-line 1553 wires, or develop short jumpers that incorporate the same function. This will allow heater and operational power for the spare SASA to be provided when necessary, but with no 1553 data insight into the functionality of the spare SASA. This insight doesn’t currently exist since the spare SASA is not powered, and is not required (but is desired) since it is a spare. (2) Don’t connect the operations power end of the Y-Jumper to the spare SASA. As a result, the RT address error won’t be possible because the SASA can’t be powered. This reduces thermal redundancy as well as 1553 communications capability with the SASA since it can’t be powered. The heaters will be the only means of maintaining the spare SASA within thermal limits. (3) Stay with current design, which is deemed unacceptable by C&DH. The ART will be recommending to Program management at the ISS Daily to remove the pins from the connectors on the Y-Jumpers as the preferred resolution option.
Video Downlink Anomaly: Early this morning, attempts were made to downlink the SSRMS video data to the ground using the Video Tape Recorders (VTRs) and Video Switching Units (VSUs). Troubleshooting is ongoing.
New IFIs Generated Within the Last 24-Hours
None
Today’s Events (GMT 2001/166):
PAO events and crew conferences.
Refresh of ORU EEPROMs (tentative)
Upcoming Events for GMT 2001/167-168 (i.e., Friday, Saturday, Sunday):
Crew time has been allocated to support SSRMS movement and grappling operations on Saturday.
Other Upcoming Events:
SASA / Spare SASA / EAS Connectivity Issues ART – Friday, June 15, 8am, MER Conference Room
SSRMS ART — June 14, 2:00 pm, MER Conference Room
Vacuum System ART — Friday, June 15, MER Conference Room, 2:00 pm
RWS ART – Friday, June 15, 1pm, Building 30, Room 2312
Tuesday, June 19 – Upgrade to new web-based IFI Database, ~3pm
