STS-131: Discovery returns home for perfect landing at KSC
Discovery has returned to Earth on Tuesday, ending the highly successful STS-131 mission at the orbiter’s home base of the Kennedy Space Center (KSC). The opening KSC and Edwards Air Force Base opportunities were waved off on End Of Mission plus one day (EOM+1), as controllers waited for acceptable weather in Florida.
The first landing opportunity related to KSC, which would have called for a deorbit burn at 6:28am Eastern, resulting in a descending node entry over North America and the US’ eastern States, for a landing at 7:34am.
With that opening opportunity waved off, and the next landing possibility in California refused, the second KSC landing opportunity was the focus, as weather began to improve. A GO was given for the deorbit burn, as Discovery began her journey home, ending in a perfect touchdown on the Shuttle Landing Facility (SLF).
Discovery had enough onboard cryos and consumables to wave off all five attempts, in the unlikely event weather on both coasts proved to be unacceptable.
“The crew performed a Group C power down to conserve cryogenic consumables in an attempt gain another day of margin. An additional day will allow more flexibility for landing opportunities over the next few days,” noted Mission Evaluation Room (MER) status on L2.
“A waste water dump was initiated at 108/12:17 GMT (13/01:56 MET) and completed at 108/12:25 GMT (13/02:04 MET). Approximately 26 lbm was dumped. A condensate dump was initiated at 108/12:37 GMT (13/02:16 MET) and completed at 108/12:49 GMT (13/02:28 MET).”
Via the Group C powerdowns, several items will be powered back on during the deorbit prep list. MER managers outlined that all systems were healthy prior to power down, as Discovery continues to perform exceptionally well during her long mission.
“GPS performance has been nominal throughout most of this period. At 108/09:56:20, after FCS (Flight Control Surface) checkout, MDM FF2 was powered down as part of the modified group C power down, and GPS data became invalid and could not be analyzed from that point forward.
“The receiver status bit (V74X8500E) from OF2 is still valid and shows that the receiver is still on and tracking satellites. MDM FF2 is planned to be powered back on as part of de-orbit preps. There are no issues being tracked by the GPS team.
“All DPS (Data Processing System) systems performing nominally. All passive thermal control systems are performing nominally and all monitored temperatures are remaining within acceptable limits. The PPCO2 level was at 1.80 mmHg during LiOH change out at GMT 109/04:50.”
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Entry Flight Direct Brian Lunney noted that he would only take the Californian landing option should KSC weather also look bad on EOM+2 (End Of Mission Plus Two Days – Wednesday), as every effort is made to return Discovery to her home port – especially considering the strain on turnaround of both the orbiter and MPLM Leonardo for STS-133. In the end, the preference of KSC found acceptable weather for her return.
However, had should weather in Florida failed to improve to acceptable levels, the ever-ready Dryden team would have been ready to host the veteran orbiter for up to a week of processing and preparation for her cross-country journey on top of the Shuttle Carrier Aircraft, as they did for her previous landing at the conclusion of STS-128.
“We’re on standby 24/7 from launch until landing. Every morning, the Landing Support Office has a telecon. We have all the [CONUS] sites [on the telecon], so we have KSC, WSSH, and us,” noted George Grimshaw, Chief of the Shuttle and Flight Ops Support Office at Dryden, via an exclusive interview with NASASpaceflight.com’s Philip Sloss.
“So they provide us mission status, they give us our weather forecast for the next two to three days, and then they typically give us the PLS (Primary Landing Site) assignment.
“Typically, by the day that you’re having the meeting, you already know who PLS is, unless there’s been a change – [in which case] they’ll typically sent out an email saying ‘the weather has changed, so we’re changing the PLS site.’ Typically, it stays the same, and then during that telecon they’ll give you [who is] PLS for tomorrow and they’ll typically throw in the next couple of days just for planning purposes. If you looked at it, we’re PLS about 80 percent of the time.
“Two hours before landing, they [the Air Force] turn the airfield over to us. At that point, all of the aircraft operations on base come to a halt. When we give them the word that it looks like we might get called up, if they have any airplanes up flying, whether they are Air Force, NASA, other tenants here on the base, they call all those people back in and they get them on the ground here or at another airfield, and then two hours before landing they turn it over to us.”
Had Discovery headed to California, she would have landed on the temporary concrete runway – either 22 or 04 – as would have been the case for STS-130. The main concrete runway, Runway 04R/22L (the “outside” runway), is undergoing another period of maintenance
“With two [concrete] runways – and of course now the main runway is closed – if we have two runways available, then they can open up the other runway up for limited operations,” added Mr Grimshaw, who went on to explain their landing day schedule.
“Typically what happens is, the navaids and landing guys come in five hours before landing. They have to be out there (on the runway) and have all their stuff set up and ready to go We have a T-38 and one of the STA airplanes comes in, they’re flying approaches and checking out the weather – and so they like to fly those systems and that way they can make sure the word gets back to the crew (about) what they’re experiencing and how things are looking.
“The rest of the convoy will typically come in about four hours ahead of time. The (convoy) vehicles are pre-staged for the most part. They can come in, they can start them up, they can do any systems checkouts that they need to do…and be ready to roll to when it’s time to roll. Basically, they like to have them in place and staged for the landing within an hour before the landing.
“Typically, they’ll start the burn as the convoy commander is doing his briefing at the fire station, and then the guys drive out (to the runway). And that’s another impact to the base – that hour before landing, there’s no movement on the airfield. If you’re not on base, you’re not coming on the base.”
Had Mr Lunney made a decision to send Discovery for a short vacation in California, communication would have played a major role for the Dryden team, from deorbit to landing.
“That’s one the roles that I play in our mission control room here. I’m the communications link between the flight director and the convoy commander during de-orbit burn through landing and even post-landing,” added Mr Grimshaw.
“We have the air-to-ground links established, so when the convoy commander is talking to the vehicle commander – the Shuttle commander – they’re doing that over air-to-ground. And they typically pipe that information from Dryden back to JSC and I think to KSC.
“In the control room, I have the flight director net, I have all the nets, everything, but the convoy commander doesn’t have that. He has the air-to-ground (and) he has all the convoy nets – he has the command net, we call them the purge and cooling nets. The convoy commander operates on (the) command net, USA ops – who is the USA equivalent of the convoy commander – operates on purge, and then the cooling net is just a backup net.”