By Dr Marc Rayman
Pasadena - August 24, 1999 - Deep Space 1's mission to test high-risk, high-payoff technologies is complete. DS1 tested 12 advanced technologies so that future missions would not have to face the cost and risk of being the first users of the new systems.
DS1 took the risks so that future missions would not have to. And now that the mission has exceeded its challenging objectives of evaluating technologies, it is turning to the job of conducting science.
DS1, which has to its credit a wealth of technology testing and a bonus asteroid encounter, was scheduled to end on September 18. But earlier this month, NASA approved an extension to the mission.
Now it is important to keep in mind that this continuation of the mission is threatened as long as NASA's budget remains in jeopardy, as it has been since a committee in the House of Representatives voted to cut NASA funding recently.
The Congressional debate on the budget is not yet complete, but if the outcome is not favorable for NASA, the consequences to DS1, and many other important and exciting space projects, may be grave.
But if the funding is available, DS1 will combine its advanced technologies with the experience of the encounter with asteroid Braille to conduct two very exciting encounters with comets in 2001, both of which were described in the last report.
To prepare for this encore, less than a day and a half after passing the asteroid, DS1 resumed thrusting with its ion propulsion system, with AutoNav firmly at the helm.
It is now on its way to Comet Wilson-Harrington, which it will reach in less than 1.5 years. DS1 will travel almost 1.9 billion kilometers, or over 1.1 billion miles, from its encounter last month with asteroid Braille to its appointment with Comet Wilson-Harrington.
The journey will take it once around the Sun, with its ion propulsion system thrusting most of the time. As devoted listeners to these recordings know, the ion propulsion system has proven itself to be wonderfully efficient.
In September 2001, DS1 will sail past Comet Borrelly, one of the most active comets that regularly visit the inner solar system.
At DS1's current distance from the Sun, each day the ion engine pushes on the spacecraft enough to change its speed by slightly less than 15 miles/hour. But day after day, week after week, the effect of the exquisitely gentle thrust builds up.
During the 9-month technology testing phase of the mission, the ion propulsion system thrusted for a total of 2.5 months. That was enough to test this important technology and to propel DS1 to its encounter with asteroid Braille.
In all that time, the ion propulsion system consumed only about 11.5 kg, or about 25 pounds, of xenon, yet its steady push was enough to change the spacecraft's speed by well over 1500 miles/hour. DS1's orbit around the Sun took it over 600 million kilometers, or about 375 million miles, from Earth to Braille.
The spacecraft has been thrusting for the past 3 weeks, and it has another 16 months of powered flight ahead, spread out over the next year and a half. In that time, it will consume most or all of the remaining 69 kg (152 pounds) of xenon.
The cumulative effect of that thrusting will be enough to change the spacecraft's speed by another 4 kilometers/second, or nearly 9000 miles/hour. That will get the explorer to its planned meetings with the two comets. The tiny probe will travel another 1.8 billion kilometers, or more than 1.1 billion miles, around the Sun by the time it reaches Comet Borrelly.
Deep Space 1 is now about 38% farther away from Earth than the Sun is and 538 times as far as the moon. At this distance of 206 million kilometers, or 128 million miles, radio signals, traveling at the universal limit of the speed of light, take almost 23 minutes to make the round trip.
Deep Space 1 Reports From Spacer.Com
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