STS-93 at Twenty Years: Planning to launch Chandra

by Philip Sloss

Just a few days from the thirtieth anniversary of Apollo 11, the mission that landed the first Americans on the Moon, the countdown for Space Shuttle mission STS-93 started at the Kennedy Space Center (KSC) in Florida. Liftoff of Shuttle Orbiter Columbia from Launch Pad 39B was planned for early on the morning of July 20, 1999, almost a full day prior to the exact time that the first bootprints were made at the Sea of Tranquility.

Now, not quite twenty years ago today, the Shuttle mission that launched the Chandra X-Ray Observatory reaches its twentieth anniversary coincident with the golden anniversary of the first human lunar landing. STS-93 also marked the first NASA human spaceflight mission to be commanded by a woman; Air Force Colonel Eileen Collins was the first woman to fly in the right seat on the orbiter flight deck as pilot on STS-63 and STS-84, and she was named flight crew commander in 1998 a year before the flight.

STS-93 was a little bit of a throwback mission, the final one to fly with the Inertial Upper Stage (IUS) in its payload bay. The heavyweight IUS deploy missions were typically shorter duration; after a Flight Day 1 deploy of Chandra and IUS, the plan was for Columbia and crew to return to Earth and land at the Kennedy Space Center in Florida after a minimum nominal mission duration of five days.

From FAWG to FRR

The Advanced X-Ray Astronomical Facility (AXAF) was one of NASA’s Great Observatories, along with the Hubble Space Telescope (HST), the Gamma Ray Observatory (GRO), and the Space Infrared Telescope Facility (SIRTF). Like HST all the spacecraft were subsequently renamed, and all were originally intended to launch on the Space Shuttle, when NASA planned to launch almost everything with its reusable, low Earth Orbit, spaceplane fleet.

Although long in planning, the Shuttle mission to launch AXAF was formalized only a couple of years prior to planned launch.

“The customer comes to NASA and says hey we want to fly something and they fill out a form like everybody else and it gets massaged into the system, so that’s a couple of years in advance,” Bryan Austin, Lead Flight Director for STS-93, said in a recent interview. “As soon as there’s something that NASA has put into the manifest which again may be a couple of years out we assign from the operations standpoint the first few lead persons to follow that flight, the lead flight director and then there will just be a couple of people assigned that I’ll work with directly.”

Credit: NASA.

(Photo Caption: The near-term Space Shuttle manifest in June, 1997, a few months before STS-93 was officially “baselined.” Although not yet official, tentative mission parameters had already been analyzed and penciled in by this time. The manifest shows Shuttle missions in transition from standalone missions to focusing on support of International Space Station assembly and logistics.)

“Back then with Shuttle, [it’s] the Payload Officer and the Flight Activities Officer that helps to build the flight plan and the mission plan, so those are the two other key people with me. And then there’s a whole team of people doing the flight design: what the mission trajectory is going to look like, how many days it’s going to be, and they have their template through the different production cycles that they go through.”

From the Shuttle Program standpoint, the payload started in the Flight Assignment Working Group (FAWG) manifest, a living document of long-term mission planning, including a general sequence of missions and orbiter assignments. Closer to the launch date, mission-specific planning baselined STS-93 in the Flight Definition Requirements Document (FDRD), where mission details like crew size, orbiter and vehicle configuration, and flight duration get their initial formal definition.

“I’m named and the initial planning starts about a year and a half to two years out,” Austin said. “The crew gets named maybe the earliest about a year out, they start their training for the flight maybe more generically maybe about six months out, but about three months out from the flight the collective team is really focusing on the specifics of the mission and the specific training for the mission and then that brings us up to the launch.”

According to the Space Shuttle Missions Summary Book, the mission was baselined in May, 1997, with a launch date at the end of August, 1998.

Credit: NASA.

(Photo Caption: A group picture of the STS-93 flight directors. Bryan Austin (left), the lead, and John Shannon, (ascent/entry) are seated. Behind them are Charles Shaw (left) and Robert Kelso.)

Michel Tognini was the first member of the crew assigned to STS-93 in November, 1997. “[He] was announced several months before the rest of the crew, due to an event NASA had with France, and they decided to announce him early,” Collins said in an email. “The rest of the crew was announced in March 1998.”

Collins selection as the first female commander of a NASA human spaceflight mission was historic, and was made by First Lady Hillary Clinton at the White House on March 5, 1998. The rest of her crew was also announced by NASA at that time; joining Commander Collins and Mission Specialist Tognini were Pilot Jeffrey Ashby, and Mission Specialists Steven Hawley and Catherine “Cady” Coleman.

“Commanders are sometimes asked about their crew, other times not,” Collins said. “For the Chandra mission, I discussed the crewmembers with management, but did not select them.”

“I believe Steve Hawley was a good, grounding element to that crew,” Austin noted. “He had a lot of experience, he’d done deploys before, he’s a Hubble guy.”

“Eileen had flown before but it was her first command, Cady had flown and she’s experienced. That was Jeff’s first time, I believe first flight as a pilot.”

Credit: NASA.

(Photo Caption: An image of the STS-93 crew in the mid-deck of a Shuttle trainer, in launch and entry suits. From left to right are Astronauts Michel Tognini, Catherine Coleman, Jeffrey Ashby, Eileen Collins, and Steven Hawley.)

“I just thought it was a great crew, I couldn’t have asked for a more experienced and ready crew and we worked great together, building the flight rules and just discussing what-ifs and whatnots and Eileen was just outstanding as the commander and her team coordinator,” he added. “It was a fun bunch, they were just all very, very easy-going.”

“This was just a great mix of people, I really enjoyed them. I went to Paris not long ago and my wife and I met with Michel at his house and had dinner with him. It’s just fun to still connect with everybody.”

The orbiter assigned to STS-93 was Columbia; OV-102 was maybe not the easiest choice for the mission, but may have been the only choice.

“This was the heaviest payload that a Shuttle will ever carry up and much less deploy and so when it came time to [choose] what vehicle to put it on, initially the folks wanted to avoid Columbia because it was the heaviest vehicle and it had a lot of the instrumentation on it from its early flight test days,” Austin explained.

“As luck would have it, or the priorities of other flights and some of the early Station activity, our vehicle got changed to Columbia.”

The other three orbiters in the Shuttle fleet were all pointed at the upcoming International Space Station (ISS) assembly sequence.

During Orbiter Maintenance and Down Periods (OMDP) in the mid-1990s back in their final assembly plant in Palmdale, California, Orbiters Discovery, Endeavour, and finally Atlantis were modified to support ISS assembly and logistics.

Credit: NASA.

(Photo Caption: The STS-93 primary payload of the Chandra X-Ray Observatory (top) attached to its IUS upper stage fills the length of Columbia’s payload bay just prior to the doors being closed for launch in July, 1999.)

One of the major changes was trading in their original internal airlock for one positioned externally to the crew module in the payload bay; the external airlock also supported the Orbiter Docking System (ODS) that was used first on missions to dock to the Russian Space Station Mir and then to the ISS. Although early ISS assembly flights fell behind original schedules dealing with issues on both American and Russian elements, by the time the full flight crew for STS-93 was announced in early 1998 Discovery and Endeavour had already returned to service from their OMDPs and Atlantis was in Palmdale for hers.

Columbia still had an internal airlock, which gave the mated AXAF and IUS payload the full length of the payload bit to fit; they still took up almost the entire length.

Lead flight director roles and responsibilities

“Largely I’m focusing on the mission plan and the flight rules and the crew and the flight team readiness,” Austin said regarding his lead flight director position. One area impacting the mission plan that Austin followed closely was adapting Columbia to carry AXAF and IUS; Columbia had never been assigned an IUS launch before.

Columbia was a little heavier structurally than the younger orbiters in the fleet, and as mentioned a significant amount of Development Flight Instrumentation (DFI) wiring and equipment remained deployed throughout the vehicle.

“One of our biggest constraints that we had was for RTLS (Return to Launch Site). We have constraints on how heavy the vehicle can be to be within the envelope of making that a viable an abort and this vehicle was too heavy.”

“So that was a ‘black zone’ — if we had to abort RTLS and being too heavy then by design the Shuttle would not survive that,” “That was really the main driver that we had to get the weight down so that we could close out those black zones for RTLS, which the Kennedy folks did. That was one of the biggest things that we worked through in the overall hierarchy of just the mission production, getting the vehicle ready.”

Credit: NASA.

(Photo Caption: A generic Return-To-Launch-Site abort profile.  This was considered the riskiest of the intact in-flight Shuttle aborts, but was certified if there had ever been an early, single-engine shutdown.  For STS-93, Columbia went through a significant weight reduction program to allow the orbiter to safely return to the KSC launch site for an emergency landing with the Chandra/IUS payload.)

“There’s a flight integration manager that is really looking to do the higher level production schedule integration between the orbiter at KSC and its production flow getting ready, the payload customer getting their payload on its schedule to get ready and put together, and then the operations team and so and I’m right up there with the program working through the issues that we had and we ran through our own series of issues just with the vehicle.”

Austin also noted other early items that came up during mission planning. “One of the big things that we knew early on with AXAF is it’s going to be very thermally sensitive,” he said.

“If you look at the shape of it, it’s this long tube and all of the smarts are down on the other end, but it’s very sensitive to the Sun since it was designed from a Sun and a thermal standpoint to be pointing in a particular direction and to be able to manage itself.”

The standard IUS mission would deploy the upper stage with its payload on Flight Day 1, but backup opportunities on subsequent orbits (revolutions) or flight days were always planned for insurance. “The Shuttle cargo bay is pretty constrained [thermally] and then especially as we’re getting ready for deploy so that presented a whole lot of analysis and iterations on how we could tap dance and weave our way through the couple of revs (revolutions or orbits) of the things that we needed to do with the payload [and] getting it OK’d to be thermally adequate to make it through deploy,” Austin explained.

The Chandra X-Ray Observatory in the Vertical Processing Facility at KSC in March, 1999. Credit: NASA.

“The biggest challenge was if we had to get to a Day 2 deploy we would have to do some other thermal tap dance to be prepared for that, so those were some of the bigger issues that we worked through with the payload.”

“My other large pre-mission job other than overseeing the timeline is building our flight rules,” Austin explained. “Each flight has a document, the flight rules, which are really all of our mission decisions that we think of ahead of time — ‘if-then-else’ kind of stuff.”

“We get the approval from the program that this is the level of risk that we’re going to take and if this problem happens, here’s how we’re going to react to it. It beats the heck out of trying to have those discussions in real time when the clock’s counting so we always have a flight rules product that the flight director authors and gets approved up through the NASA hierarchy of the Shuttle Program.”

“So that’s the biggest thing that we worked on and that goes through a myriad of reviews,” he added. “We’ll have regular team meetings with the customer and ourselves and talking about what-ifs and we’ll do some analysis along the way to justify if that can even work, so that document is greatly important and that’s really what helps to drive a lot of simulations too.”

“The SimSup (Simulation Supervisor) can look for those pressure points — he knows you’ve been in a discussion about ‘well, if this happens’ and he can tell if we’re not sure what we’re going to do. Then he knows he needs to exercise that in a sim and put in that failure or that scenario and get us to be really firm in our decision, or maybe help us to understand there’s more to it than that and come back and readdress it.”

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