STS-123: Friday meeting clears UHF radio to fly as-is

by Chris Bergin

Managers met again this morning to clear the final few issues ahead of the start of the STS-123 launch countdown operations (S0007) – which begins in the early hours of Saturday.

Engineers also carried out work early this morning on the UHF radio system to gain additional data on the problem, ahead of the management meeting which subsequently cleared the radio to fly as-is.

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STS-123: UHF Radio Issue:

The UHF radio is used for air-to-air communications on a variety of mission elements, from EVAs, to biomedical data, to the final part of re-entry.

Given the system fault is not currently breaching a Launch Commit Criteria (LCC), it should not affect the procedure towards an on time start of S0007 on Saturday morning.

However, yesterday’s meetings failed to fully clear the UHF radio from no further work, as additional data was required for Friday morning’s management discussion.

‘UHF transceiver power amp failure update: No decision was made at the Noon Board yesterday,’ noted Friday morning processing information on L2. 

‘The Noon Board will reconvene this morning at 1000L (delayed to 11am) to further discuss additional troubleshooting and the option to remove and replace the radio.

‘The schedule shows time for that work today on 2nd Shift pending engineering evaluation.’

To gain additional data for this morning’s meeting, engineers carried out additional tests on the UHF ATC XCVR element of the radio.

‘Plan is to demate connectors from the UHF ATC XCVR and monitor the lines going in and out of the radio,’ noted memos outlining the work that was carried out overnight.

‘This is being done in an attempt to verify there are no external stimulus that would cause the internal box failures we are experiencing. This will require the installation of breakout boxes and strip chart recorders.

‘The UHF system will have to be powered up and cycled through the different modes. At the completion of the testing a SCAN retest will be required on all demated pins.

‘Paper is currently in work to demate the connectors and install the breakout boxes. We will need help from the repair depot (JSC) to determine how much current should be expected on each pin so we can size the fuses in the breakout boxes correctly.’

The Noon Board meeting – which rarely actually occurs at noon – met again on Friday morning (11am), following yesterday afternoon’s discussions, and cleared the UHF radio to fly as-is.

Presentations from that meeting will be summarized later today.

Pad Flow:

The vehicle is now pressurized for flight, as per S0071 operations (Hypergolic/Main Propulsion System pressurization). 1st stage pressurization was completed yesterday morning as scheduled.

Final pressurization was completed last night at 02:22 (local). The pad was reopened for controlled work at 02:30.

Engineers at the pad also successfully replaced the L8 solenoid valve – following the GHe load/vent sequencer’s momentary pressure increase on the RRCS (Right Reaction Control System) fuel He (Helium) tank.

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