ANSWERING THE CHALLENGE!

Last week in CQ #4: GO TELL IT ON THE MOUNTAIN, we asked: Olympus Mons is the highest feature on Mars. What is its counterpart on Earth? Be forewarned: it is not Mount Everest! ANSWER: If you measure Mauna Kea, Hawaii, from ocean floor to peak, you will find that it is higher than Mt. Everest, Nepal -- about 30,000 feet compared to Everest's 29,000 feet. In last week's BONUS QUESTION we asked: If you think about how astronomers measure the height of features on Mars, you'll have a clue to help you answer this question. What do we mean? ANSWER: For Mars, astronomers use the "datum level" -- the reference surface at which atmospheric pressure is 6.1 millibars (the pressure at the triple point of water) -- to give a baseline for measurement of altitude. On Earth we use sea level, but as CQ#3 reminded us, that would currently be impractical to do on Mars -- though some astronomers think there may once have been an ocean on Mars, or at least lakes of liquid water, now lost to space or locked in permafrost.

NEW CHALLENGE FOR THE WEEK

CQ #5: BRUSH UP ON YOUR GREEK! There is a letter of the Greek alphabet that is very important both to launching NASA's current Mars missions and to getting to Mars. What is that letter? Also, explain how it is used. You are invited to send original student answers to: jwee@mail.arc.nasa.gov. Please include the words CHALLENGE QUESTION in the subject line of your email. The kids' names will be listed online and token prizes will be given to those will the best answers. Answers are due within seven full days of Challenge Question posting. (e.g. If a CQ is posted on April 18, answers are due by midnight PDT on April 24.) A list of answers from all students who submitted them will be posted on the Live From Mars Web site soon.

APRIL WEBCHAT SCHEDULE

Wed. April 23, 9 a.m., PDT: Guy Beutelschies, test director for the Mars Pathfinder spacecraft, Jet Propulsion Laboratory, Pasadena, Calif. Guy's job involves leading a team that tests the spacecraft to make sure everything works! Tues. April 29, 10 a.m., PDT: Bridget Landry, deputy uplink systems engineer, Mars Pathfinder, Jet Propulsion Laboratory, Pasadena, Calif. Bridget teaches computers on the ground to speak the same language as the Mars Pathfinder.

ONLINE CHAT WITH FAMOUS WOMEN

Female leaders from a broad spectrum of professions have been invited to participate in NASA's second annual Virtual Take Our Daughters to Work Day on Thurs. April 24 from 6 a.m. - 4 p.m., PDT. To view the schedule, profiles and registration information go to the Women of NASA Web site at http://quest.arc.nasa.gov/women/intro.html

LIVE BROADCAST REMINDER!

Mark your calendars for Thurs. April 24 when Passport to Knowledge will be broadcasting, live, "Cruising Between the Planets."

LOOKING FOR STUDENT QUESTIONS

For the April 24 Live From Mars broadcast, there may be time to feature student questions that are submitted before the broadcast. Student questions should relate directly to the themes covered in this broadcast: Mars Global Surveyor, Mars Pathfinder and Sojourner, navigation and trajectory maneuvers, and careers. Questions may be submitted to phaddon@aol.com no later than Sun. April 20! Include student's name, grade, school, town and state. Also, send a copy of the question to: question-lfm@quest.arc.nasa.gov

PATHFINDER MISSION STATUS

[Editor's note: This status report was prepared by the Office of the Flight Operations Manager, Mars Pathfinder Mission, NASA Jet Propulsion Laboratory.] 11 April 1997 The spacecraft remains in good health and is currently about 71 million kilometers from Earth. The only spacecraft activities performed this week were a regular ASI/MET health check, a Heat Rejection System Pump B cycle, and some modification to Attitude Control Subsystem fault protection parameters. The total flight time since launch is now 128 days, and we have 85 days until Mars arrival. We successfully completed an operational readiness test of all activities from Mars entry -2 days through Sol 2. This test was performed using the Pathfinder Testbed and Mars Sandbox. The Mars approach phase included periodic updates to the Entry, Descent, and Landing flight software parameter set and execution of a contingency Trajectory Correction Maneuver #5. We are investigating a minor problem which occurred during airbag retraction, which did not significantly effect the test. The surface operations test included a planned failure of the High Gain Antenna and subsequent Low Gain Antenna operations.

GLOBAL SURVEYOR FLIGHT STATUS

[Editor's note: This status report was prepared by the Office of the Flight Operations Manager, Mars Surveyor Operations Project, NASA Jet Propulsion Laboratory.] Friday, 11 April 1997 This week, the Mars Global Surveyor science team received an unexpected bonus from the Sun due to a solar flare eruption that took place on Monday. Eruptions of solar flares occur when disturbances deep within the Sun's interior cause streams of electrically charged atomic particles to be ejected from the solar surface. These charged particles move through the solar system at speeds in excess of 1,000,000 kilometers per hour. In order to allow the science team to study this event, the flight team sent commands to Surveyor that enabled the spacecraft to record solar flare data gathered from the Magnetometer science instrument. These commands activated the spacecraft's data recorders late Wednesday afternoon, about half a day before the stream of charged particles from Monday's eruption reached Surveyor. Although past occurrences of solar flares have both disrupted space communications and damaged spacecraft, Monday's eruption was relatively mild in comparison. The Mars-bound Surveyor spacecraft sustained no damage from the solar flare. Late Thursday afternoon, the navigators on the project canceled the trajectory correction maneuver that was planned for later this month. This maneuver would have refined the flight path to Mars by slightly altering the spacecraft's speed and velocity. However, analysis showed that this month's maneuver involves a velocity change of only 40 millimeters per second (less than one-tenth of a mile per hour). The maneuver was canceled because with such a small velocity change, the errors in executing the maneuver are comparable to the size of the maneuver. This canceled maneuver would have been the third of four planned maneuvers during the journey to Mars. The first two occurred in November 1996 and March 1997. The fourth trajectory correction maneuver will take place on August 25, 1997. Yesterday marked the halfway point in the journey to Mars with respect to time of flight. As of April 10, Surveyor has completed 154 of the 308 days required to reach the red planet. The halfway point in terms of distance between the Earth and Mars occurred last week on Monday, March 31. This difference in halfway dates arises from the fact that the positions of the two planets constantly change during the spacecraft's journey to Mars. After a mission elapsed time of 155 days from launch, Surveyor is 68.43 million kilometers from the Earth, 48.55 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 24.98 kilometers per second. This orbit will intercept Mars 153 days from now, slightly after 6:00 p.m. PDT on September 11 (01:00 UTC, September 12). The spacecraft is currently executing the C6 command sequence, and all systems continue to be in excellent condition.

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