Deep Space 1 Mission Update 14 Feb 2001

Deep Space 1 Mission Update: Dr. Marc Rayman’s Mission Log

Thank you for visiting the Deep Space 1 mission status information site, for 120 weeks consistently the number 1 site among sentient life forms in the local group of galaxies for information on this mission of exploration and adventure. This message was logged at 12:15 pm Pacific Time on Sunday, February 11.

DS1 continues to operate extremely well on its remarkable
travels through deep space. While it requires a great deal
of careful planning and diligent monitoring to keep the
distant probe happy and healthy, the smooth sailing has
allowed the operations team to devote its energies to
putting the finishing touches on upgrades for the craft’s
software. DS1 already has been reprogrammed four times
during its voyage, each time to outfit it with new
capabilities so that it could blaze new trails. The latest
version of software, which goes by the sure-fire
market-grabbing name M6F3, will give the spacecraft some
enhancements to improve its chances of acquiring science
data during the comet encounter in September that will be
the extended mission’s risky but exciting finale. In
addition, a few improvements to make the craft easier to
operate will be included, and some minor bugs that have
been discovered in the current version of software will be
corrected. (Of course, there aren’t any major bugs, as the
software on board now has allowed the spacecraft to fly
nearly flawlessly since it was loaded 8 months ago.)

To prepare the software, experts test it in a Deep Space 1
simulator at JPL. This facility includes some devices that
are similar to what is on the real spacecraft. Other
systems are recreated with software simulations, and
together they all operate with another set of software that
allows the system to behave as if it were in space. It is
not a perfect recreation of the actual spacecraft in the
space environment, but it does allow commands that will be
sent to the spacecraft to be checked out first, and in this
case it allows the main computer’s new software to be
tested.

Next month, M6F3 will be loaded on the spacecraft. The Deep
Space 1 project has reserved extra time for this with the
Deep Space Network, NASA’s worldwide array of huge antennas
for communicating with remote spacecraft. The week of March
5 will be devoted to beaming the files with the software
across the solar system to DS1, then the following week
will be used to install it on the craft’s central computer.
This log will be updated on about March 18 with a report on
the outcome of the complex and delicate process of
uploading the software, rebooting the computer to begin
running it, verifying its performance, and returning the
craft to its operational configuration. You can look
forward to finding details that will be available nowhere
else in the solar system, including what kind of take-out
food was provided to the operations team for the day that
requires virtually all team members to be at their stations
in the DS1 mission control center.

March might hold even more of interest for all Deep Space 1
fans than the tricky replacement of the software. The
Learning Channel and the BBC may be broadcasting a
documentary on the mission. (If we can learn the broadcast
day and time in advance, we will try to put it on the DS1
Web site.) Although your devoted correspondent hasn’t seen
it yet, with material like this, how could it be anything
other than thoroughly captivating? The documentary will
focus on the primary mission, which concluded in September,
1999.

As faithful readers throughout the cosmos know, one of the
many significant accomplishments of the primary mission was
the testing of an advanced ion propulsion system. That
system is still being used now, and on January 27, it had
accumulated 365 days of operation. In that year of
thrusting, the exotic system consumed only about 44 kg, or
97 pounds, of xenon propellant. Even though for a variety
of reasons the propulsion system has occasionally been
operated in less efficient modes, it still has managed so
far to impart the equivalent of 2.6 kilometers/second, or
about 5800 miles/hour, to DS1. In fact, the real function
of the ion propulsion system is to change the shape of Deep
Space 1’s orbit around the Sun; a recording in about 4
months will explain more about this with some interesting
new statistics you can use to impress members of species
less familiar with the complexities of orbital mechanics.

DS1 spends most of the time now in powered flight toward
the comet encounter; it turns once each week to point the
main antenna to Earth for a few hours of communications
before turning back to the preselected thrust direction.
Those turns however consume hydrazine, the conventional
rocket propellant it uses to rotate or hold itself steady.
To help conserve the dwindling supply of this precious
resource, we would like to reduce the amount of turning the
spacecraft has to do. Engineers recognized that one way to
accomplish this would be to arrange it so that the
orientation of the spacecraft when it is thrusting is the
same as when the antenna is pointed at Earth. In that case,
no turns would be necessary to conduct the two separate
activities.

As DS1 fires its ion engine to reach the comet, and Earth
and the spacecraft move rapidly in their separate orbits
around the Sun, how can we guarantee that some of the
thrusting occurs while the antenna is pointed to Earth?
Well, the ion engine and the main antenna are already
bolted onto the craft, so it’s a little late to change
their separate pointing directions, so we need an alternate
solution. Another way, of course, would be simply to move
Earth so that it is aligned with wherever the antenna
happens to be pointing, but with the very small budget for
the Deep Space 1 project, the cost of completing the
Environmental Impact Statement for that was considered
prohibitive. But ever-resourceful engineers devised a less
expensive strategy.

The flight plan for DS1 includes throttle levels and
directions for firing the ion engine at certain times, all
carefully balanced and choreographed to guide the probe to
the comet. In early January we computed what the
orientation of the spacecraft would be at all times
throughout February if the antenna were pointed at Earth,
then we determined what the effect on DS1’s orbit would be
of thrusting in those orientations, and finally we adjusted
the flight plan for January so that the combined effect of
thrusting in January and February accomplished the desired
effect.

In essence, the craft has a slight zigzag in its flight
profile. After zigging in January, the zag in February ends
up with the main antenna facing Earth while the ion engine
is firing to help the spacecraft close in on the comet. Now
this does not mean we can constantly stay in touch with our
remote but dear friend. The Deep Space Network is kept very
busy maintaining its highly complex and finely tuned
systems while it keeps Earth in contact with far-away
robotic explorers. But whenever DSN time is scheduled for
communications with Deep Space 1 this month, we can receive
data without having to turn the craft, thus preserving the
hydrazine for future needs.

DS1 is now about 280 million kilometers, or 175 million
miles, from comet Borrelly. Each day, as they separately
speed toward their September meeting, their separation
shrinks by nearly 1.8 million kilometers, or 1.1 million
miles.

Deep Space 1 is 2.2 times as far from Earth as the Sun is
and about 860 times as far as the moon. At this distance of
330 million kilometers, or 205 million miles, radio
signals, traveling at the universal limit of the speed of
light, take over 36 and a half minutes to make the round
trip.

Thanks again for logging in!