CONTOUR Mission Status Report August 19, 2002 — 4:00 p.m. (EDT)

CONTOUR Team Listens For A Signal

With electronic eyes and ears pointed to the sky and a fix on CONTOUR’s
location more than 1.3 million miles (2.1 million kilometers) from Earth,
the mission team continues checking for a signal from the spacecraft.

“The plan is to watch and monitor,” says Mission Director Dr. Robert
Farquhar of the Johns Hopkins University Applied Physics Laboratory,
which built CONTOUR and manages the mission for NASA. “We realize the
possibilities are small, but we can’t discount the idea that the
spacecraft is still operable. We have to determine that before we give
up.”

Since Friday the team has received telescope images from several
observatories showing two objects traveling along CONTOUR’s predicted
path – which engineers believe is CONTOUR and part of the spacecraft
that may have separated from it when CONTOUR’s solid rocket motor fired
on Aug. 15. Mission operators at APL and navigators at NASA’s Jet
Propulsion Laboratory are using these images to pinpoint the spacecraft’s
orbit and are aiming the Deep Space Network’s powerful 70-meter and
34-meter antennas along that trajectory.

“Without knowing how big the objects in the telescope images are, we’re
going to work on the assumption that the spacecraft may still be largely
intact,” Farquhar says. “You need at least three separate observations
to determine an orbit, and we have that. We know we’re looking in the
right place.”

This week, mission operators are listening to determine if CONTOUR is
alive and can carry out a timed command to cycle and attempt to transmit
through three of its four antennas. The sequence is timed to start
96 hours after CONTOUR receives its last command. Because the team can’t
determine which commands the spacecraft may have received late last week,
the cycling between transmitters and antennas could have started as early
as 4:09 (EDT) this morning or could start as late as 10:09 (EDT) tonight.

The 60-hour sequence begins with the first of CONTOUR’s two transmitters
cycling 10 hours each through the low-gain and multidirectional (pancake)
beam antennas on CONTOUR’s aft side – opposite the dust shield – and the
forward-side low-gain antenna. (Because of its narrow beamwidth and the
unlikely prospect of its facing Earth, CONTOUR’s high-gain dish antenna
is not part of the sequence.) The second transmitter then repeats the
pattern.

“It may be difficult to hear anything because, depending on the
spacecraft’s position and condition, the antennas might not have a direct
line of sight toward Earth,” says CONTOUR Mission Operations Manager Mark
Holdridge. “But we’ll be listening.”

If the team doesn’t hear from the spacecraft this week, Farquhar says, a
final concentrated effort will be implemented in December when the antennas
are in a more favorable orientation. “We’re obligated to give it this last
try,” he says. “And who knows, we might get lucky.”