Live From Mars was active July 1996-December 1997.
STUDENT SLEUTHS PARTICIPATE IN P.E.T. MYSTERY SITE ACTIVITY
Hundreds of students from grades 3-12 are now engaged in solving the "Where in the World Are These P.E.T. Mystery Sites?" -- an enrichment activity developed as a fun and challenging follow-up to the LFM Planet Explorer Toolkit activity. The Mystery Site activity models the "Launch Phase" data collection by presenting data and images from five mystery sites found somewhere in the world. The goal is for students to analyze the data and images, compare what is known about the sites in terms of weather, flora, fauna, soil, rock, water, etc., and decide the specific location of each of the five sites. Students are also using the Planetary Data Input shared online by participating P.E.T. classes (who analyzed their own unique sites) as a base for comparative data analysis to help narrow the possible mystery site locations. Different levels of difficulty provide an ever-challenging task for upper grade levels. Students of the elementary grades receive a multiple-choice answer form allowing them to select the mystery site location from three known locales. Middle-school students select from a possible five known locales and high-school students receive a range of latitude and longitude within which the sites are located. High-school students must identify the sites by latitude and longitude based on their analysis of data. The mystery site activity is open to all students, regardless of past participation in the Planet Explorer Toolkit activity. Prizes will be awarded to winners from each grade level. Classes must register for participation by sending email to: firstname.lastname@example.org. Please include the following information: - name of sponsoring educator - location of school/homeschool, etc. (Give full mailing address) - number of students participating, age and grade level - email address of sponsoring educator NOTE: If you are the coordinator registering for several classes, you may send one email with a list of the classes, grade level/age, number of students, and sponsoring educator. A full overview of the Mystery Site Activity is online at: http://passporttoknowledge.com/lfm/teachers/mystery.html This activity is open for participation through May 20, 1997.
MARS TEAM JOURNAL #1: Burning the Midnight Oilby Bridget Landry [Editor's note: Bridget is a deputy uplink systems engineer on the Mars Pathfinder team. She takes complex, but general computer programs and makes them understand all the commands that the Pathfinder knows.] April 22, 1997 Working graveyard shifts this week, going in to work around 9 p.m., and coming home with the dawn. Strange to be driving home under rosy skies, pulling the pillow over my head to shut out the morning light. Stranger still to hear meetings called for midnight or 2 a.m. and having to ask, honestly, whether something scheduled for 6 is a.m. or p.m. Oddly enough, what I learned of myself and my own tolerances, at science fiction conventions (when I tried to stay up all night, for fear that I would miss something) has actually helped me in these tests. I know, for instance, that I can either go without sleep, or go without food for an extended period of time, but things get real surreal if I try to do both. Snacking all night keeps my blood sugar up, helps me concentrate. Small things are important: I brought in slippers so that my feet are comfy and so I can sit Indian-style in my chair more easily. And I find that the hardest time is between 2 and 4 a.m.--my mind starts to wander and follows odd routes to the strangest places. I have to keep reminding myself of the immediate task at hand. I take copious notes, both to keep from forgetting something (my memory goes as the hours advance) and as a focus to stay on track, or return to the track when I've taken a mental stroll. This test hasn't gone well. Many mistakes on all sides have added up to some major concerns. I think it will all sort itself out; from my own experience, early rehearsals are often disastrous. I think the telling point will be how much and how fast we learn from this, and whether we can keep making new mistakes, rather than repeating old ones. Seventy-two days and counting... MARS TEAM JOURNAL #2: "Hey Navigator... Wheres the Spacecraft?" by Pete Kallemeyn [Editor's note: Pete is the navigation team leader for the Mars Pathfinder spacecraft. he is responsible for determining where Pathfinder is, predicting where it will go in the near future, and determining the means to correct the path in order for us to reach the surface of Mars on July 4!] April 29, 1997 This is the first in a series of four journal entries that details the steps the NAV team and others go through to plan, design, test and execute a trajectory correction maneuver (TCM), which is a major activity for a spacecraft in cruise. Today the NAV team is to perform orbit determination and maneuver computation for the third mid-course maneuver. The design of the maneuver, a critical event during interplanetary cruise, is a process that takes a few days to complete. I hope to step you through the whole process in four journal articles. This first one is a bit long because it deals with orbit determination, my specialty, so forgive me if I talk a bit too long... The first step in designing a maneuver is to determine where the spacecraft currently is and accurately predict its motion until arrival. That process is referred to as orbit determination, which is a complicated process, but I'll try to explain it as best I can. Basically, we start with a computerized model of the spacecraft's trajectory that our navigation software can process. The numbers from the computer model should closely represent the actual trajectory that the spacecraft is flying, but it's not perfect. In order to make it as perfect as possible, we use tracking data to measure the real trajectory and adjust the computer model accordingly. Tracking data for Mars Pathfinder consists of two types, Doppler (a measure of how fast the spacecraft is receding from Earth) and range (a measure of the distance from the station to the spacecraft). There are other types of possible tracking data types, but on Mars Pathfinder we prefer to use only Doppler and range to reduce operational complexity and spacecraft resources. The Deep Space Network measures the range and Doppler from the stations to the spacecraft at regular intervals, and the results make their way to the NAV team in the form of a "Tracking Data File." The NAV team reads the file and compares the actual tracking data values with values we would expect from our model. Any error in our trajectory model will show up in the tracking data, and our programs know how to adjust the model to match the data correctly. This may sound straightforward, but it's really not, for a number of reasons. First, there are a lot of physical effects that affect the spacecraft's flight path through space. Gravity of the Sun and the planets is the most obvious, but there is also a small but continuous acceleration due to the photons from the Sun hitting the spacecraft. Solar radiation pressure is what this is called, and it has been a difficult effect to model for us until just recently. There are also small changes in velocity that occur whenever the spacecraft's thrusters are fired to change the attitude, and we can't forget the results from past TCMs. Secondly, since we use tracking data to help determine our trajectory, we need to know what phenomena will affect the measuring and collecting of that data. This includes the locations of the stations on the surface of the Earth, the orientation of the Earth at the time the measurement is made, the effect of the atmosphere and the ionosphere on the signal from the spacecraft to the station, and finally the electronic delays in both the spacecraft hardware and the station components that collect the data. That's quite a lot of stuff to keep track of, but is necessary in order to obtain the best possible trajectory solution. Finally, we have to be careful to check the tracking data before using it, because sometimes we get bad data that could mess up our solution process. So the art of orbit determination sometimes involves editing out bad data, adjusting slightly flawed data, and reporting these errors to the Deep Space Network, who needs to know how they are doing. Orbit determination is also experimental in nature. The NAV team will try different strategies in orbit determination, always looking for the right one. Sometimes we'll use only Doppler data and ignore the range, or maybe we'll try the opposite. Sometimes we'll try estimating a particular effect and see what the result is, or we might choose to leave it unmodelled. A lot of comparisons between solutions are done, and this is where the human element of "judgment" comes into play, something you can't really program into software without a lot of effort. Experience with orbit determination is very important to know if you've got a good solution, an okay solution, or a bad solution. After a number of experiments have been tried, we'll select a few of the better experiment results for consideration in selecting the 'right' solution. Today, for example, we had four possible solutions to pick from. All of these solutions were within 10 kilometers of each other, so we really could have picked one at random and had a good solution virtually guaranteed. Yet we prefer to discuss briefly any advantages or disadvantages a given solution might have, and narrow down the field to one solution. This we did in a meeting around 11:15 today. After discussing the various aspects of each solution and the implications of each for maneuver design, we selected one that Robin Vaughan had done. Its 'code number' was 970429rv104630, which identifies it among the many solutions we've done to date. I figure, I have done over 500 solutions since launch, so you can see that we need some method to keeping track of all these solutions. Now we know where we are... The next step is to determine where we want to go, which is the subject of the next entry.
WHAT TO EXPECT AT THE LANDING
Really, truly, "live" from Mars This July 4 and in the weeks thereafter, expect to see extensive coverage of Pathfinder's landing on TV newscasts, in print and on the Internet. NASA-TV plans minute-by-minute coverage on landing day, with actual footage intermixed with press briefings. Several networks are planning special coverage. The LFM Web site will provide updates as we learn more. And remember, the LFM Teacher's Guide provides suggestions for Activities you can undertake before school ends to "set" students up to appreciate the events of this summer. Let us know how this works! (And if you're district has summer school, by all means participate from class.) Coming soon to a science center near you... In addition to headline reports in the mass media, Live From Mars and its partners from the American Museum of Natural History in New York, Mississippi State University and The Planetary Society (TPS), plan special live, interactive TV programs to be offered via satellite on July 6 and 9, from 2-4 p.m. Eastern (11 a.m.-1 p.m. Pacific.) July 6 will not only feature the events of the first two days on Mars, the best color enhancements of the first pictures returned and a chance to hear NASA scientists' first reactions, but also the TPSs "Planetfest" -- a combination Star Trek convention and celebration of space exploration and scientific discovery, promising a good time for all! To be held in Pasadena, Calif., just a few miles from the Jet Propulsion Laboratory on July 4-6, we plan to link "Planetfest" in via video to JPL, New York, and many other live locations around the nation. It's hoped that CU-SeeMe, real audio and other Internet technologies will also share "Planetfest" and the events of "Landing Week" with those unable to access satellite TV. Though primarily designed for participation by youngsters, families and camp groups in science museums and planetariums (since school is out for the summer in most places), anyone with access to a movable satellite dish can obtain the programming. Many science centers are already planning events around Pathfinder's landing. We expect many will integrate Live From Mars into this, but we can't promise or predict. Please check locally and if your local museum doesn't yet know about what's going on, share what you know with them, and direct them to our Web site, which will have increasingly detailed information. Stay tuned and use Live From Mars to link directly to the very latest from the Red Planet!
[Editors note: This status report was prepared by the Office of the Flight Operations Manager, Mars Surveyor Operations Project, NASA Jet Propulsion Laboratory.] Friday, May 2,1997 No major activities took place this week. For the past three weeks, few activities have occurred because the Surveyor spacecraft has been configured in a quiet state for a search campaign to detect gravity waves. According to theoretical physics, these waves are gravitational disturbances emitted by all objects in the universe. However, because gravity is a relatively weak force, detection of these waves is almost impossible unless they are generated by massive objects such as black holes and matter at the center of the Milky Way Galaxy. To date, nobody has ever detected a gravity wave. If Surveyor encountered these waves, the spacecraft would experience an extremely small jolt. This tiny bumping motion would cause a tiny shift in the frequency of the spacecraft's radio signal transmitted to Earth. Analysis of the data generated by this experiment will take six months or more. After a mission-elapsed time of 176 days from launch, Surveyor is 92.74 million kilometers from the Earth, 37.03 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 23.89 kilometers per second. This orbit will intercept Mars 132 days from now, slightly after 6:00 p.m. PDT on September 11 (01:00 UTC, September 12). The spacecraft is currently executing the C7 command sequence, and all systems continue to be in excellent condition.
[Editors note: NASA Press Release #97-85] NASA's Mars Global Surveyor spacecraft can safely and successfully aerobrake into its final orbit around Mars this fall with its one partially deployed solar panel in a modified configuration, mission managers have decided. No special maneuvers will be conducted to attempt to force the array to latch, and the focus of the Surveyor engineering team now will turn to minor modifications to the critical aerobraking phase that will circularize the spacecraft's orbit for the beginning of two years of science operations. "After careful analysis of the situation, we've determined that the solar panel on Mars Global Surveyor that is not fully deployed presents very little risk to the mission," said Glenn E. Cunningham, Mars Global Surveyor project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. The decision by NASA's flight team at JPL and its partners at Lockheed Martin Astronautics, Denver, CO, was reached after several months of extensive analysis of spacecraft data, ground-based computer simulations and a series of very slight spacecraft maneuvers that were carried out in January and February to characterize the situation. "Thanks to an early launch that gave us an advantageous trajectory, we will not have to aerobrake into the Martian atmosphere as fast as we had originally planned to reach the mapping orbit, and that will reduce the amount of heating that the solar panels undergo during this gradual descent," Cunningham explained. "We will rotate the solar-cell side of the panel that is not fully deployed by 180 degrees, so that it faces into the direction of the air flow that exerts drag force on the spacecraft as it dips repeatedly into the atmosphere," he said. "This way, the unlatched panel will not be in danger of folding up onto the spacecraft's main structure, nor will the panel be at any greater risk of heating up too much." The solar panel in question is one of two 11-foot wings that were unfolded shortly after Surveyor's Nov. 7, 1996, launch from Cape Canaveral Air Station, FL. Data suggest that a piece of metal called the "damper arm," which is part of the solar array deployment mechanism located at the "elbow" joint where the entire panel is attached to the spacecraft body, probably was sheared off during deployment in the first day of flight. The lever that turns the shaft became wedged in a two-inch space between the shoulder joint and the edge of the solar panel, leaving the panel tilted at 20.5 degrees from its fully deployed and latched position. Although the situation was never considered a serious threat to accomplishing the science objectives of the mission, the tilted array caused the JPL/Lockheed Martin flight team to re-evaluate the aerobraking phase, in which the spacecraft must rely almost solely on its solar panels for the drag needed to lower it into a nearly circular mapping orbit over the poles of the planet. This phase of the mission will begin a week after Mars Global Surveyor is captured in orbit around Mars on Sept. 11, and will last approximately four months. Aerobraking was first tested in the final days of the Magellan mission to Venus in October 1994. The technique is an innovative method of braking which allows a spacecraft to carry less fuel to a planet and take advantage of the planet's atmospheric drag to descend into a low-altitude orbit. Mars Global Surveyor will use an aerobraking phase much like that used to circularize Magellan's orbit. The solar wings -- which feature a Kapton flap at the tip of each wing for added drag -- supply most of the surface area that will slow the spacecraft by a total of more than 2,684 miles per hour during the four-month phase. Surveyor's orbit around Mars will shrink during this phase from an initial, highly elliptical orbit of 45 hours to a nearly circular orbit taking less than two hours to complete. Engineers determined that the deployment springs currently holding the tilted solar panel in its nearly deployed position will not be strong enough to withstand the forces of aerobraking. To solve that problem, they designed a new configuration in which the tilted solar panel, along with the deployment springs, will be rotated 180 degrees, using a motor-driven inner gimbal actuator, and held in position with force applied by an outer gimbal actuator. Sequencing software will be modified to turn the gimbal actuators on before each closest approach to the planet and off at the conclusion of each drag pass. As a consequence of the new aerobraking configuration, the more sensitive cell-side of the unlatched wing will be exposed directly to the wind flow of atmospheric entry, requiring that aerobraking be done in a more gradual, gentle manner. Ground tests have demonstrated that the unlatched solar panel will have more than adequate thermal margin to withstand additional heating as the spacecraft circularizes its orbit for the beginning of science mapping in March 1998. Meanwhile, Mars Global Surveyor continues to perform very well on its arcing flight path toward the red planet and its arrival in orbit. A third, very minor trajectory correction maneuver, planned for April 21, was deemed unnecessary and canceled. In addition, science instrument calibrations continue to go well, and plans are being prepared to take an approach image of Mars a few days before the July 4 landing of Mars Pathfinder, which passed Mars Global Surveyor en route to Mars on March 14, 1997. Mars Global Surveyor is the first mission in a sustained program of robotic exploration of Mars, managed by JPL for NASA's Office of Space Science, Washington, DC.
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