Discovery undocks – return mapped out

by Chris Bergin

Shuttle orbiter Discovery and her crew have undocked from the International Space Station (ISS), ahead of Friday’s return to Earth.

The Mission Management Team (MMT) meeting once again considered a Thursday return, but with the need for a full late inspection on orbit, Discovery will choose between one of three landing sites to get her wheels back on the ground on Friday.

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Returning on Flight Day 14 means Discovery has the Kennedy Space Center, Edwards Air Force Base and White Sands at her disposal, with a wave off only occurring in the unlikely event that of a weather constraint at all three sites, or a technical issue arises during the deorbit preps.

‘Boeing, USA (United Space Alliance), and NASA Engineering to develop a strawman list of what needs to be performed to support a possible landing at White Sands,’ noted one of a series of NASA memos acquired by this site, as NASA gets all the landing sites on standby.

Earlier today, NASA management once again considered the Thursday landing possibility, with Late Inspection the main element under evaluation.

Even though Discovery has been cleared from any worrying damage on her TPS (Thermal Protection System), Late Inspection allows for imagery to be taken to ensure the orbiter has not received any subsequent damage whilst docked to the ISS, with MMOD (Micrometeoroid/Orbiting Debris) damage still one of the highest risks orbiters can receive on orbit, as seen by the example of the MMOD strike on Atlantis during STS-115 earlier in the year.

‘Late Inspection Discussion: There is an MMT FD 11 or 12/19 at 1pm,’ added another memo earlier today. ‘They will be discussing risk trades of late inspection and the preservation of a weather wave off extension day.’

The inspections will take up most of Flight Day 12, with Flight Day 13 consisting of Flight Control System checkouts and RCS (Reaction Control System) hotfire testing, before the landing on Friday afternoon.

As Discovery departed from the ISS, she performed only a half flyaround, which is related to both the timeline, and the reduction of consumables/propellants, used during taking over attitude control from the ISS during the recent solar activity on orbit.

The mission for Discovery has been relatively trouble-free, with only a couple of minor issues noted during the flight. One issue, with the Flash Evaporator System (FES) won’t be troubleshooted during the next two days, due to the timeline. However, the system is working fine on its Primary A loop (PRI A).

‘Entry Flight Director has said no to the FES troubleshooting,’ noted another memo. ‘Timeline is too crowed to accommodate.

‘OPO (Orbiter Project Office) was briefed on the FES troubleshooting and Entry Flight Director has said that the timeline is too tight to add the FES troubleshooting. We will go home on PRI A.’

Meanwhile, Shuttle manager Wayne Hale added to the praise that has been commonplace during this mission, making his comments via the report’s writer on this week’s Shuttle Stand-up/Integration Summary.

‘Mr Hale is extremely pleased with the support for this mission. The NASA Administrator had many good words on how well he feels the Shuttle Program in particular is doing. Mr. Hale said this is due to the combined efforts of the NASA and contractor workers and management around the country.

‘Mr. Hale is proud of the way everyone has picked up to an operational pace this year, and is looking forward to a great 2007.’

Discovery undocked from ISS at 5:09pm, after a total docked time of 7 days 21 hours. Discovery backed away from the ISS PMA-2, then performed a partial flyaround at 400-600 ft.

A 1.5 ft/s separation burn followed at 6:01pm on the -V bar (behind the ISS), a second at 6:40pm, and a third at a second at 7:15pm, increasingly more powerful, as Discovery and the ISS gained separation from each other over the coming few days.

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