Managers considering May 11 for STS-125 – ET camera/flash troubleshooting

by Chris Bergin

The dual processing flows for Atlantis and Endeavour are proceeding to plan, with the main engineering focus on the ET camera flash system, which is undergoing troubleshooting on Atlantis. Managers have also completed the review of the SSP (Space Shuttle Program) Flight Readiness Review (FRR), with evaluations taking place on advancing the launch date by one day to May 11.

Processing Flow Latest:

With two vehicles out at the launch pads, engineers are primarily working towards launching Atlantis from Pad 39A on STS-125, while processing Endeavour to a standby point on Pad 39B, in case of a LON (Launch On Need) requirement – an unlikely event where Atlantis suffers serious damage on orbit and requires rescue.

“S0600 vertical payload operations: Payload Bay doors were opened at 1032 EDT,” noted processing information on Tuesday via L2. “Power up was completed at 0224 EDT. Cap stow complete and rain gutter removal in work at 0430 EDT.

“APU re-pressurization is complete to date with 24 and 48 hour leak checks in progress. LH2 storage tank replenishment is scheduled for today. Two waves of tankers are expected.”

Atlantis’ pad flow remains on target, allowing managers to consider an advancement of the launch date to May 11. Evaluations are in the early stage of planning, with engineers being consulted on their confidence on achieving the advancement.

The plan is related to the Delta IV/GOES launch – which is also scheduled for STS-125’s current launch date of May 12 following recent delays. Due to range requirements, it is understood the plan would be to delay the Delta IV launch enough to allow Atlantis three launch attempts – starting May 11.

Opening requests for flow status were sent to the KSC teams during the SSP FRR, which has completed its two day review of the mission. 32 presentations from the SSP FRR are available on L2, multiple articles will follow ahead of launch.

ET Camera/Flash System Troubleshooting:

a49The main issue being worked at the pad relates to the ET umbilical well camera and flash system on the belly of the orbiter – which is used to take photography of the separated External Tank after MECO (Main Engine Cut Off).

This allows for imagery to be downloaded on the ground, and used to pinpoint foam loss – some of which may have impacted the orbiter during the ride uphill – in order to cross reference any debris relates issues during the DAT (Damage Assessment Team) process.

The problem with the camera/flash system has occurred on a few recent flights, including STS-119, when the flash only worked the one time, while the resulting imagery could not be downloaded as planned.

“The digital umbilical camera used on STS-119/15A was x-rayed and it showed a blown five-amp fuse. An electrical overload caused the failure,” added processing information on the issue, which appears to be fleet-wide, given smaller issues with also noted on system during Endeavour’s processing for STS-127/400.

“Special topic discussion at FRR – for reasons why it is safe to fly this camera – will be brought forward. Issues with the camera already on STS-125 are being studied for common causes.”

The issue with Atlantis’ system relates to a communication issue – as seen with one of STS-119’s problems with the downloading of imagery – which was initially put through a troubleshooting process by changing the software, which failed.

“ET camera communication problem. Update: A new laptop software load did not make a difference during troubleshooting,” added processing information. “The original communication issue remains unresolved. More troubleshooting to follow. JSC engineering is consulting.

“The camera ‘manual bracket’ setting could not be confirmed. Engineering is looking at a possible internal failure of the camera.”

By late on Tuesday, engineers decided that the camera system will have to be removed from the orbiter for a closer inspection. However, that process is reasonably complicated.

a216The system has to be removed through ET door cavity, so engineers will have to pull the ET umbilical baggie back by removing the retainer brackets, or slit the baggie and tape it up afterwards.

“Such a procedure has been carried out in the past, but there are concerns about the baggie kapton plastic being thicker where the tape is applied and if that would damage tiles as the baggie rips away,” noted one engineer explaining the process. “This issue is being worked, but the forward plan is to replace the camera.”

The Orbiter Project Office (OPO) at JSC also provided an update on the status of troubleshooting late on Tuesday, which confirmed that the flash on the system is working as required, which means it is not suffering from a full system failure.

“Performed operation to verify function/non-function of the camera by stationing an observer to watch for flashes during the picture acquisition period. A total of 23 flashes were observed. This proves the camera is capable of taking pictures,” noted information acquired by L2.

“The camera team will review the results of this test, as well as a functional test of the GSE (Ground Support Equipment) on the other (Endeavour’s) camera and make a determination as to the next course of troubleshooting at ET sep telecon on Wednesday.”

It is not currently known if this issue is a constraint to launch, especially with elements of the camera system – such as being able to take images – working as required.

Meanwhile, good news has been reported on processing information in relation to the shipping of Atlantis’ Flow Control Valves (FCVs), which are on a deadline of the end of the month for installation into the orbiter.

Click here for articles on the FCV issue since STS-126.

“Status of GH2 Flow Control Valves for STS-125. All three FCVs are scheduled to be on site 4/28. Installation is planned for 4/29, and retest on 4/30.”

Discussions are still taking place on whether a modification – which involves the installation of a protective bracket on the outside of the 90 degree bend, immediately downstream of the valves – will be requested for STS-125. More will follow on this story in an upcoming FCV forward plan article later this week.

L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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