NASA
researchers are one day away from testing what they hope will be the space
agency's first unmanned vehicle capable of meeting up with other orbiting
spacecraft. That is, as long as the weather holds.
Launch
officials said Monday that there is a 90 percent chance weather violations could
scrub the Oct. 26 launch of DART, a spacecraft designed to seek out and
rendezvous with a satellite in Earth orbit. If successful, DART's
flight could prove key technologies developed by NASA to build autonomous,
rendezvous-ready spacecraft.
"We have
launched on 90 percent chance of violation days before," NASA launch director
Omar Baez said during a prelaunch press conference
today at Vandenberg Air Force Base in California.
If weather
does scrub the launch, a second attempt could occur as soon as Thursday, he
added.
DART, short
for Demonstration of Autonomous Rendezvous Technology, is expected to launch
from the air atop a four-stage Orbital Sciences Pegasus XL rocket at 2:13:20 p.m.
EDT (1813:20 GMT) in a flight staged
from California's Vandenberg Air Force Base. A former passenger jet, Stargazer
L-1011, will carry the rocket into launch position 40,000 feet (12,192 meters) above
the Pacific Ocean.
"We're running
on a lot of excitement...but we don't want to jeopardize all the money and effort
into this mission," said Jim Snoddy, DART project manager
from NASA's Marshall Space Flight Center, of the $95 million mission. "We want to
make sure it goes safely."
NASA
researchers believe the autonomous capabilities tested by DART will lay the
foundation for future missions beyond Earth orbit, where an autopilot - instead
of real-time remote control - may be more preferable during dockings. The
mission is cooperative effort between NASA researchers and the Orbital Sciences
Corporation (OSC), which developed the spacecraft.
"Whether
you're going to the moon or Mars, you're always going to have to put things
together in space," Snoddy said.
Spaceflight sans humans
While DART's launch marks the first flight of a U.S.-built
unmanned rendezvous space vehicle, though the Russian Federal Space Agency's
Progress and Soyuz vehicles have docked autonomously with space stations for
years. Europe is also planning to launch the cargo ship Jules Verne, the first
of its Automated Transfer Vehicles (ATV) to the International Space Station
next year.
"DART
carries it to the next step," Snoddy said, adding that
once the spacecraft launches, it will be function independent of any human
intervention. "We're automating everything from the ground operations to the flight
operations, and we don't heavy antennas or flight boxes."
At the heart
of the DART mission is a device called an advanced video guidance sensor (AVGS),
which combines advanced optical and electronic ranging systems to approach its
satellite target - the Multiple Paths Beyond Line-of-Site Communications
(MUBLCOM) spacecraft launched in 1999.
A global
positioning system (GPS) will also aid DART's
rendezvous, and onboard software will test collision avoidance maneuvers, and
direct the spacecraft to fly circles around MUBLCOM. An onboard camera will
hopefully catch images of the rendezvous.
"We've done
everything we can on the ground," Snoddy said. "The
next step is to take it into space."
Air-to-space rocket
It should
take DART and its Pegasus booster about 12 minutes to rocket into space once
their Stargazer mothership drops them 100 miles (160 kilometers)
out over the Pacific Ocean.
Once in
orbit, DART is programmed to begin using its GPS system to establish its
location then fire three hydrazine thrusters to chase its target satellite. The
MUBLCOM spacecraft carries two sets of reflectors for DART to bounce ranging
lasers off of, researchers said.
When DART
flies within 621 miles (1,000 kilometers) of MUBLCOM, it is expected to switch
over to its AVGS navigation system and hopefully fly rings around the
spacecraft, with its closest approaching reaching about 16 feet (5 meters)
before backing out and making another pass. About 24 hours after launch, DART's onboard batteries should begin to expire and the
spacecraft will fire its engines self-destruct reentry path to burn up in Earth's
atmosphere.
After DART's flight, researchers hope to study the data and apply
it to future technology shakedown missions, including automated docking
missions.
"This technology
will become more important as we get farther away from Earth," Snoddy said.
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