Live From Mars was active July 1996-December 1997.
WEBCHAT WITH DAVID MITTMAN
Weekly WebChats offer an opportunity for your students to virtually meet the people on the front lines of the Mars exploration adventure. Teachers have reported that the chats really enliven students' enthusiasm. Next week our guest will be David Mittman from NASA's Jet Propulsion Laboratory in Pasadena, California. He will discuss his role in planning the Mars Pathfinder's activities and in sending commands to the spacecraft during its flight to Mars. (MPF will be launched Sunday, Dec. 1, 11 p.m. EST.) David's chat is scheduled for Tuesday, December 3 from 9-10 a.m., PST. To join in the fun, point your Web browser to http://passporttoknowledge.com/lfm/events/interact.html to follow the links to the *moderated* chat room for experts. If you plan to participate in this event, please RSVP to Andrea by sending a brief email note to andream@quest.arc.nasa.gov telling her that you plan to join the session. This RSVP is very important, as it will allow us to ensure that the chat room does not become overly crowded. To best prepare, please have your students read the biography of David before the WebChat: http://passporttoknowledge.com/lfm/team/mittman.html A schedule for the December WebChat's will be published shortly. Watch the LFM Web site for the date and time of next week's chat.
CHALLENGE QUESTION #7: ARRIVING AT MARS AT DIFFERENT TIMES
Recently we asked: The Mars Global Surveyor (MGS) takes off in November and is scheduled to arrive at Mars between September 11-22, 1997. The Mars Pathfinder (MPF) takes off sometime in December. No matter when it leaves, it is scheduled to arrive on July 4, 1997. Why does the Pathfinder get to Mars earlier, even though it leaves later? And how can the Pathfinder have an exact arrival date even though its lift-off date may vary? Answer from Cheick Diarra: There are several reasons for Pathfinder's earlier arrival at Mars. Pathfinder is much smaller and lighter than Mars Global Surveyor. As a result, the rockets sending it to Mars can get it going at a faster velocity. Also, Pathfinder goes on a much more direct route to Mars than MGS, which takes a longer, more looping path. So not only is MPF going faster, it has less miles to travel. There is a good reason for MGS's more looping path. The arrival velocity depends on the type of trajectory. The more looping trajectory provides a slower arrival velocity. Since MGS is an orbiter, NASA wants it to arrive at Mars with as little speed as possible. This is because it will need to be slowed down with a retro burn to be captured by Mars' gravity. That maneuver is called the Mars Orbit Insertion maneuver, or MOI for short. The slower MGS is going relative to Mars, the smaller the retro burn. And a smaller retro burn mean less fuel (and weight and dollars). So that is why MGS is on a more looping trajectory which will allow for a slower arrival speed. MPF, on the other hand, is not going into orbit, so it can arrive at a faster speed, and thus its more direct route to Mars. To help understand why a more looping trajectory results in a slower arrival speed, consider a golf ball being putted on a slanting green toward the hole. A golfer can hit the ball hard right toward the hole and the ball will arrive relatively quickly. Or else, the ball can be putted more gently toward the uphill side of the hole; in that case, the ball will loop down towards the hole and arrive at a slower speed. Finally, about the issue of the fixed arrival date for MPF. When we travel to Mars, we have the opportunity to do Trajectory Correction Maneuvers (TCMs) that let us correct not only our aim point at Mars arrival but also the time of arrival. Early on, NASA decided July 4 would be a good day to arrive. This was partially historical. In 1976 when the Viking spacecraft went to Mars, it was expected to land on July 4 for national reasons (July 4 is America's Independence Day). But when Viking arrived, there was a raging dust storm that prevented this scheduled landing so the team missed a July 4 landing and decided to remain in orbit until July 20 (July 20 is the anniversary of the first Apollo landing). So this time NASA has decided that Pathfinder should land on July 4. The TCMs for Pathfinder will be performed to remain true to the July 4 landing date. This is the last Challenge Question until sometime in March (six weeks before the second LFM broadcast in April). However, this doesn't have to be the end to sending out challenging questions. Students should make up their own Challenge Questions for each other. These are known as Student Stumpers and examples can be found in the Kid's Corner at http://passporttoknowledge.com/lfm/kids/index.html
[Editor's note: Donna Shirley is the manager of the Mars Exploration Program. Donna manages three flight projects and studies of future missions to Mars. Everyday she deals with scientists trying to understand Mars, and with the technology we need to go to Mars without costing a lot. Donna was saddened by the failure of the Russian 96 spacecraft to go into orbit and offers this account of its demise.] MARS 96 LAUNCH FAILURE Donna Shirley - http://passporttoknowledge.com/lfm/team/shirley.html November 18, 1996 We were all very sad to see the failure of the Mars 96 Russian mission to Mars, which launched November 16. At first the launch looked beautiful. I heard about it on television news, then read about it and saw pictures on CNN's web site: http://www.cnn.com/TECH/9611/16/russia.mars.update/index.html But then this morning Ed Stone, the director of the Jet Propulsion Laboratory, called to tell me that the fourth stage of the launch vehicle had only burned for a short time, the spacecraft had separated from the fourth stage, and the spacecraft was in Earth orbit instead of on its way to Mars. Mars 96 was a huge orbiter with 20 different instruments from many countries. The orbiter carried two "small stations" which were to land on the Mars' surface and make measurements, and two large penetrators which were to plunge into the Martian soil and make measurements several meters below the surface. The Russians and their international partners had worked for many years to pull the mission together. The mission was originally supposed to be launched in 1992, but had to be delayed first to 1994, then to 1996 because of lack of money in the Russian space program. If it had worked it would have been a wonderful complement to the U.S. Mars Global Surveyor mission (now on its way to Mars) and the Mars Pathfinder lander mission, which will launch December 2. There was a U.S. experiment on each of the two small stations called the Mars Oxidant Experiment, or the MOx. It was supposed to measure the chemistry of the soil to find out what was causing all the organic material to disappear from the surface. (Viking discovered this problem in 1976.) Since Pathfinder and Mars Surveyor 98 don't have this experiment it will be 2001 before we can find out why this situation exists. There is more information about the Mars 96 mission at their home page-- http://www.iki.rssi.ru/mars96/mars96hp.html On a more cheerful note, I was just on a Family Channel television show with Buzz Aldrin (the second person on the Moon) and Jack Schmitt (the next to the last person on the Moon). We talked about human and robotic missions to the Moon and Mars, and speculated about how and when humans might go to Mars. We took call-in questions from around the country. The final guest on the show was 12-year-old Josh Slavin, who has been to Space Camp in Huntsville, Alabama six times. He wants to be the first person on Mars. Also look for me on "Good Morning America," probably on November 29 or December 2.
THE PLANET EXPLORER TOOLKIT (PET) ACTIVITYNow is the time to join this exciting online collaborative activity! Over 1700 students of all ages are already registered to take part in the Live From Mars PET Activity. This activity strives to engage students in the following: - Think like the Mars Mission Team - Conduct research on scientific instruments and determine which data are most valuable in observing the environment - Deal with the constraints of big science endeavors - Use their problem-solving and critical-thinking skills - Engage in classroom debate - Prepare their best PET proposal and share online - Interact online with real planetary scientist mentor Sanjay Limaye and other experts & Passport to Knowledge staff - Learn how to reach consensus - Collect real data about their own local environment - Share data online - Interpret data and solve the PET Mystery Sites (a special online activity for all grades) - Have fun learning about the real work of scientists You are **not** too late to join! Planet Explorer Toolkit Timeline October 17-December 10: Brainstorm the Planet Explorer Toolkit and determine your proposal. December 10-December 20: Share your *best* Planet Explorer Toolkit proposal and rationale online via the debate-lfm forum. Each class may post one PET proposal. December 20-January 3: Break for the holidays January 6-January 31: Classes debate online the relative merits of the PETs presented. Advisors/mentors will be online to help moderate the discussion and help us reach consensus. Reach consensus by January 31. February 3-February 28: Classes collect data from local environments and submit their Planetary Data Input to NASA Quest for sharing online. March 3-7: PTK staff and advisors create five datasets and clues to represent the Mystery Sites for the next activity and prepare the set of clues for each grade level range (elementary, middle, high school). March 10-April 16: Classes participate in the "Where in the World are these Mystery PET Sites?" Students will also be able to participate in activities relating to interpreting the data collected. These activities will be presented at our LFM web site. April 17-onwards: This collaborative activity will remain online for all interested students, educators, parents, etc. to enjoy over the coming months as the Mars Pathfinder reaches its destination. Need More Details? Learn more about the PET Activity by accessing our Live From Mars Web site at: http://passporttoknowledge.com/lfm/events/pet.html where you will find a step-by-step plan to assist you and your students. Want to Register? All classes/groups should register by sending a note to Jan Wee, education outreach coordinator at: jwee@mail.arc.nasa.gov Please indicate: teacher or sponsor's name, grade or age of students, school name and location, and number of participating students.
FIRST LFM BROADCAST AVAILABLE ON VIDEOTAPE
