Atlantis has all eyes on Sister

by Chris Bergin

Atlantis’ mission to the International Space Station (ISS) to finally re-start assembly flights won’t just depend on whether her sister, Discovery, has a ‘clean’ STS-121.

While eyes will be on how the modified External Tank (ET) performs during ascent, with the hope that the second test flight since the loss of Columbia will see an elimination of large foam liberation, the mission itself now has the added task of repairing the ISS’ robotic systems, which will ultimately allow Atlantis to re-start assembling the orbiting outpost.

Discovery is currently set to launch on STS-121 within a window of May 10, through May 23, paving the way for another 16 flights, 15 of which will be to the ISS, one to service the Hubble Space Telescope.

Atlantis was set to follow in July on STS-115, but that mission date has been pushed back to the end of August. She will, however, be on standby to rescue the crew of Discovery, should a major problem occur during the eight and a half minute ride uphill.

While Discovery’s mission will test the new ET, and re-supply the ISS with the multi-purpose logistics module (MPLM) Leonardo, Shuttle manager Wayne Hale explained the new element of STS-121’s goals.

‘(STS-121) has changed in a profound way,’ he noted. ‘This was going to be our second test flight and a logistics and re-supply mission for the ISS. Because of the failure of the trailing umbilical system (TUS), they (the ISS) are frankly crippled in their robotic operations today.’

The TUS is a system that involves cables between the Mobile Transporter, Mobile Base System and a movable platform that allows the station’s robotic arm to move back and forth along the truss during construction and maintenance work. One of the cables was severed late last year.

‘We’ve got a new task to perform on STS-121 to re-enable the robotic systems on board the ISS so that they can support the next assembly flights,’ added Hale.

‘Quite frankly, that’s as much in the critical path, alongside the ET, doing the work in getting that payload (MPLM) on board, etc.’

One of the astronauts hoping the system is repaired during Discovery’s mission is Steve MacLean – a Canadian who will be on STS-115 with Atlantis.

The 52 year-old will be operating the Canadarm2 – ironically the first Canadian to do so – on the ISS when he arrives in the orbiter, supporting the installation of Atlantis’ cargo, the P3 and P4 trusses.

He is also – quiet obviously – keeping his eye on how Discovery’s mission progresses.

‘The scenario right now is that the next flight will be on May 10th and they have a window that lasts a couple of weeks,’ MacLean said to ‘What they’ve decided to do is slip us to August and so now our (launch) window is August 28th to September 15th.

‘We fly August 28th, as long as the next flight goes well.’

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