Spaceflight Now

NASA faces hurdles to get launch date for next shuttle
Posted: September 29, 2009

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Two upcoming satellite launches, a pair of meteor showers, multiple Russian missions and tight launch windows are causing potential headaches for NASA planners looking ahead to the next shuttle mission in November.

NASA is readying the shuttle Atlantis for roll out to pad 39A on Oct. 13 and launch around Nov. 12 on a mission to deliver critical spare parts to the International Space Station. But the ship's nine-day launch window currently is in conflict with a pair of unmanned satellite launches, one a commercial mission and the other military.

The U.S. Eastern Range, which provides tracking and telemetry support for all rockets launched from Florida, can only support one mission at a time and it operates on a first-come, first-served basis.

A United Launch Alliance Atlas 5 carrying an Intelsat communications satellite is currently booked on the range for a launch Nov. 14 with a backup opportunity the next day. A ULA Delta 4 rocket carrying a military communications satellite has the range booked Nov. 17 and 18.

NASA had hoped to launch Atlantis on Nov. 9, but that would have required Russian space managers to move up the launch of a new docking module. The Russians were unable to comply and the docking module remains scheduled for launch Nov. 10.

While those discussions were going on, the Atlas-Intelsat team booked the range for Nov. 14.

Because it takes a day or so to reconfigure range equipment to support a different launch, NASA could end up with just one day or so at the end of its window if the unmanned launches stay on track.

NASA officials are hopeful the conflict can be resolved but as of this writing, the unmanned missions remain on the range and launch preparations are continuing.

Even if the first satellite launch moves and Atlantis takes off on Nov. 12, the Leonids meteor shower is expected to peak on Nov. 17, the day the crew plans to carry out the mission's second spacewalk. Some 300 "shooting stars" per hour are expected at the shower's peak. While the shower is not believed to pose a threat to the shuttle, NASA planners are assessing whether the spacewalk can safely proceed as planned if Atlantis is able to take off on time.

The shuttle's launch window closes Nov. 20, the start of a so-called beta-angle cutout. During such cutouts, the angle between the sun and the space station's orbit results in temperature issues for the docked shuttle-station "stack." The upcoming cutout ends on Dec. 5 and a fresh shuttle launch window opens on Dec. 6.

If Atlantis is unable to take off in November, NASA will have to contend with the Geminids meteor shower during the December launch window, a shower that poses a more significant risk to the shuttle. Even though icy debris from the Leonids travels twice as fast as the rocky fragments that make up the Geminids, the latter is spread out over several days while the former is concentrated over just a few hours.

"Leonids of the same mass have four times the striking power of the Geminids," said Bill Cooke, an astronomer with the Meteoroid Environments Office at the Marshall Space Flight Center. "But ... the Geminids have a higher flux enhancement than the Leonids because it's such a big shower."

Made up of icy debris from comet Tempel-Tuttle, the Leonids are expected to produce some 300 shooting stars per hour at their peak around 2:43 p.m. EST on Nov. 17 when Earth will plow through the debris stream. Cooke said initial predictions called for up to 500 per hour and the revised rate represents an "outburst" as opposed to a "storm."

In contrast, the Geminids are believed to be made up of rocky fragments from a body known as Phaethon, which appears to be an asteroid. This year's shower is expected to peak around midnight Dec. 13-14 at a normal rate of around 120 events per hour.

"The Leonids will be an outburst with a strength 10 to 20 times normal, but as far as the environment is concerned, the Geminids meteor shower still has more meteors per area per time than the Leonids do," Cooke said. "The Geminid stream is much wider. The Leonids stream is nice and compact."

Shuttles have flown before during the Leonids and Geminids showers, but NASA planners are re-assessing the risks associated with impacts. In the case of the Leonids, sources say the concern is more about whether a spacewalk might need to be delayed if the shuttle manages to launch on time. With the Geminids, analysts will be looking at whether the shuttle should even be in orbit.

A senior NASA manager said Tuesday a slip to December for Atlantis would not have any major downstream impacts on other upcoming shuttle flights. But the window is short and closes on Dec. 13, the start of a so-called Soyuz cutout.

The Russians plan to launch three station crew members in a Soyuz capsule on Dec. 21 and if the shuttle took off after Dec. 13, the ship would still be there when the Soyuz arrives, which would violate joint safety guidelines.

If Atlantis misses the November and December launch windows, the flight would slip into early 2010.