Endeavour’s UHF radio fails re-test – no decision on forward plan

by Chris Bergin

Endeavour’s problematic UHF radio – which underwent replacement via parts donated from Atlantis at the weekend – has failed a re-test.

The Engineering Review Board (ERB) has recommended to fly as-is, though that still required approval by the Noon Board meeting, which concluded at around 4pm local time – with no decision taken. They will meet again on Friday morning.

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The issue with Endeavour’s UHF radio was noted last week, calling for parts of the system to be replaced via parts – specifically the transceiver – from Atlantis, as a solution for the upcoming mission.

Re-testing was carried out yesterday, before the pad was closed for the opening pressurization work on the Hyper/MPS systems. However, the radio is still not working in ‘high power’ mode.

‘The replacement UHF radio failed retest yesterday. Specifically, the UHF radio could not be operated in ‘high power’ mode; the radio functioned normally in the ‘low power’ setting,’ noted L2 processing information on Thursday morning. 

‘The team will discuss the test results and further disposition at an ERB (Engineering Review Board) meeting planned for today.’

Options will include further work, or fly as-is – depending on Flight Rules. It is not a constraint to entering S0007 at present.

Following the approval to fly as-is by the ERB, the Noon Board – chaired by Leroy Cain – began their meeting at 3pm local time, where a final decision on a forward plan was discussed.

The meeting concluded without deciding a forward plan, and will meet again on Friday.

Meanwhile, the shuttle is also undergoing Hyper/MPS (Main Propulsion System) pressurization – which will require an element of troubleshooting via the replacement of a solenoid valve at the pad today. Final pressurization activities are still expected to be completed by Friday.

One IPR (Interim Problem Report) has been noted during initial pressurization, which requires the removal and replacement of a solenoid valve at the pad today. This is not deemed to be a problem for completing pressurization activities.

‘Hypergolic/MPS pressurization for flight picked up yesterday. 1st stage press is expected to be complete at about 0630 – 0700; final press is scheduled for Friday 3rd shift,’ added Thursday’s processing report.

‘Picked up an IPR during initial pressurization. The GHe load/vent sequencer caused a momentary pressure to be exceeded on the RRCS (Right Reaction Control System) fuel He (Helium) tank of 3189 psig; should have been no more than 3176 psig.

‘The pressure overshoot was due to a solenoid valve (L8) which was slow to close when commanded. The constraint is to final pressurization (op 225-3). The plan is to R&R the valve on the 107 foot level and perform a retest today.

‘This should not be a constraint to picking up with final pressurization as scheduled tomorrow on 3rd shift.’

In other pad flow news, airlock closeout was completed on Wednesday, as orbiter aft closeouts continue ahead of the upcoming Call-To-Stations (CTS) for the start of the S0007 Launch Countdown activities. Installation of the 50-1&2 doors and aft confidence test are scheduled for Friday.

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