Thank you for visiting the Deep Space
1 mission status information log, widely believed to be the most popular site in any spiral galaxy for
information on this technology validation mission. This message was
logged in at 12:45 pm Pacific Time on Sunday, July 11.
Of DS1's payload of 12 advanced technologies, 11 have now received 100% or
more of their needed testing. Nevertheless, additional tests are being
conducted on many of them to assess how they fare as they continue
operating in space. The twelfth technology is the autonomous navigation
system, known to its legions of fans, which of course includes devoted
readers of these logs, as AutoNav. It is on schedule with 95% of its
required testing complete.
With most of the technology testing behind it, the team's attention has
turned to preparations for the encounter with an asteroid with the
charismatic yet refreshingly simple name 1992 KD. The primary objective of
the event will be to provide that final 5% of the testing of AutoNav. As a
bonus, now that we have already squeezed more out of this mission than was
required -- or expected by many people -- we want to do still more. As
fellow taxpayers, we can understand the desire to get as much out of this
mission as possible. So the two science instruments that DS1 has tested
will be used to gather exciting scientific data (including pictures) during
the encounter with this intriguing body. But keep in mind that this is
primarily an exceedingly challenging test for the small portion of AutoNav
that can only be exercised by visiting a solar system target.
AutoNav continues to collect images of distant asteroids and stars to
refine its estimate of where it is in the solar system using a method
described in many earlier logs. But it is still too far away from 1992 KD
to see that tiny asteroid, so for now it is simply using the best estimate
of where the asteroid is. AutoNav will not be able to detect 1992 KD until
about one day before it arrives. AutoNav has done a remarkable job
calculating its position in the solar system, now routinely getting within
1000 km or under 600 miles of the position as determined by conventional
radio tracking. Compared to its distance from the Sun this is impressive
indeed. This accuracy is comparable to being anywhere in the continental
United States and determining your position to within about 70 feet. When
DS1 is traveling through most of the expansive emptiness of the solar
system, this knowledge is more than adequate. But when it gets in the
vicinity of 1992 KD, it needs to do even better. The principal limitation
now in AutoNav's ability is the result of imperfections in the camera.
Although AutoNav has sophisticated techniques to analyze the camera's
pictures, it cannot fully compensate for the shortcomings of the camera.
AutoNav's designers and testers are paying close attention now to see how
well it can do.
The encounter with the asteroid will be relatively brief, as the spacecraft
will be passing by at 15.5 kilometers/second, or nearly 35,000 miles/hour.
The operations team has been developing the complex set of instructions
that will govern the spacecraft, including the ones that give AutoNav the
opportunity to design and execute maneuvers to correct the spacecraft's
trajectory, the commands to the new technology science instruments to
collect data, and directions to the attitude control system on how to turn
the spacecraft at the moment of closest approach. Refining this unusually
complex choreography, in which all the spacecraft systems including AutoNav
need to work together, is the focus of the small operations team's work
right now. A group of instructions is known as a sequence, and each day,
the sequences covering the final 6 hours before the closest approach to
1992 KD are run through the Deep Space 1 test facility at JPL. This is a
simulation of the spacecraft, created using some hardware similar to what
is on the real spacecraft and some computer programs that emulate the
behavior of other parts of the spacecraft. This allows the team to test,
modify, and retest sequences, a cycle repeated now nearly every day. The
test facility is certainly not identical to the spacecraft, so a successful
test does not guarantee success on the spacecraft, but it does allow many
of the bugs to be worked out. A rehearsal of the encounter using the
actual spacecraft is planned for July 13. This will be an opportunity to
compare the performance of the sequences in the test facility with the same
sequences run on the spacecraft when it is not in the vicinity of 1992 KD.
Following that, more tests will be run in the test facility. When DS1
takes the final test on the evening of July 28, it will be on its own. Its
closest approach to the asteroid will occur at 9:47 pm PDT, and it will be
several hours after that before it can begin reporting its results to
Earth. Future logs will provide more details on the events to occur at
encounter as well as progress in reaching the asteroid.
Deep Space 1 is still more than 23 million kilometers, or over 14 million
miles, from 1992 KD. The spacecraft is now more than 15% farther away from
Earth than the Sun is and over 450 times farther than the moon. At this
distance of over 173 million kilometers, or almost 108 million miles, radio
signals, traveling at the universal limit of the speed of light, take
longer than 19 minutes to make the round trip.
Thanks again for logging in!