L-2 MMT meeting debates Atlantis’ WLE sensor capability for STS-122

by Chris Bergin

Shuttle Atlantis is behaving well on Launch Pad 39A, as the countdown continues to proceed towards Thursday’s launch of STS-122.

The Mission Management Team (MMT) met to discuss the final few issues, relating to a communication issue with the WLESS (Wing Leading Edge Sensor System) and compatibility problem with the Windows XP laptops on board Atlantis.

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The WLE sensors are located underneath the RCC panels on both of Atlantis’ wings. They are used to detect impacts during ascent, allowing for areas of interest to be pinpointed ahead of Flight Day 2’s inspections with the OBSS (Orbiter Boom Sensor System).

The sensors are also used on orbit, allowing for an ability for Atlantis to ‘feel’ any MMOD strikes that are a potential threat to the panels during the mission. The sensors are extremely sensitive, to the point they read ‘ghost’ strikes, as seen on previous missions, subsequently checked out as readings that are not recordings of actual impacts.

Problems with the WLESS on Atlantis – specifically the WLE IDS (Impact Detection System) have been under evaluation for weeks, with all attempts to make the sensors communicate with the flight deck of Atlantis failing.

However, an engineering effort has managed to get the sensors working to a point where they can be programmed for flight, allowing the possibility of data being used via ISS assets, should it be required.

‘On WLE impact detection system, are getting to the point where we can program sensors; this took big integrated effort between the JSC Engineering team and KSC Operations Engineering team; was an excellent effort. JSC Engineering team attempted to build a unique concept using very small patch antenna. Attempted to download data from sensors in the aft flight deck, but couldn’t,’ noted the latest Stand-up report.

‘Are essentially done with the WLESS. It will collect and store data and download it when back on ground. Only programmed to take ascent data. In event of failure of OBSS or inability to collect data using OBSS system, there is potential to use ISS wireless instrumentation system to collect data from sensor packages and download to ground. Don’t know yet if this would work, and would only try if have failure and think might want to get the data.’

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The other issue – also known since Atlantis was stacked inside the VAB (Vehicle Assembly Building) – relates to the ET umbilical camera, which isn’t downloading imagery to the onboard laptops – upgraded to Windows XP on STS-120 and subsequent flights.

‘Still cannot download images from ET umbilical camera. Based on lighting plan, this is a moot point. Were able to download images using an A31p laptop loaded with Windows 2000 successfully, unlike with Windows XP. Will do one more test to revalidate this assumption. Appears difference between Windows XP and Windows 2000 is most likely root cause.’

That solution to the laptop compatability issue is set to be in place in time for STS-123.

‘On the Windows XP issue, identified that it is caused by the difference in Windows 2000 and Windows XP,’ added the information. ‘The camera is set at a lower data rate than Windows XP likes. A software change is needed; will have until STS-123 to pick this up.’

The only issue at the launch pad has been a leaky valve on the Ground Support Equipment (GSE), which will be replaced after Atlantis heads to the International Space Station (ISS).

Leaks at the pad are commonplace with the aging infrastructure, though they mainly have no effect on the continuation of pre-launch activities. The latest relates to a valve on the backup leg of an O2 Panel.

‘Pressure Operated Valve on the pad O2 Panel is Leaking when Valve is Closed,’ noted a processing report on Tuesday morning.

‘During engineering walkdown, the pressure operated valve on the pad GO2 830-1 panel (90 ft level) was observed to be leaking when the GO2 battery was brought on-line. This valve is on a backup leg and is normally not used during S0007.

‘There are two regulators and one iso valve downstream of this valve, which is normally left open during countdown. FCP plans on leaving the leaking valve in place for the remainder of S0007 and R&R it afterward.’

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