January 1997
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| January 1997 |
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NASA is returning to the Red Planet - this time with a tiny, six wheeled rover to explore the rocky surface. Pathfinder, a combination lander-rover was launched in December and is scheduled to reach the surface of Mars on July 4 1997.
Pathfinder's payload will deliver a lander to study the Martian landscape and weather conditions and a tiny rover which will explore dozens of metres from the parent lander. The rover will allow Earth-bound scien-tists to study the surface lying beyond the view of an immobile lander.
The rover, nick-named 'Sojourner', is an experiment to test ideas proposed soon after Viking landed on Mars in 1976. If the rover functions for more than the hoped-for seven Martian days and continues to work for 30 more days then its design may be used for other missions to Mars and to other planets and moons in the solar system.
In Sojourner's 16kg shoebox-sized frame are three cameras, an autonomous navigation system and an instrument for sampling the chemistry of nearby rocks. The power for the rover's systems is provided by solar panels covering the top of the rover. However this need for solar energy means that Sojourner can only travel between 10am and 2pm local time when the sun light is of sufficient intensity. The miniature cameras on board will photograph the landscape in colour and black and white showing details less than a millimetre across.
The rover will also carry an Alpha Proton X-ray Spectrometer, APXS, mounted on a retractable, steerable boom tipped with a radioactive source. The source will cover the surrounding area with alpha particles. The instrument will look for anything which reflects the particles and hence discover the mineralogical nature of the terrain. The APXS can also be used to detect any elements in a sample emitting protons or X-rays.
Controllers on Earth will examine how hard each of the rover's six wheel motors must work in order to move Sojourner along. This data and photo-graphs of the rover's tracks will help soil dynamicists deduce the mech-anical properties of the Martian soil.
The rover is controlled via the Pathfinder lander. Immediately after landing cameras will radio panoramic views of the surface back to Earth. Scientists will use stereo pictures taken by the lander to plan Sojourner's course over the four hour period. The rover will then begin to explore the surface at a rate of 1 mph. Radio signals will take more than ten mins to get from Earth to Mars, soSojourner is designed to negotiate rocks as high as 13cm in case ground controllers miss any large obstacles on the planned route. All of this happens within the sight of the lander whose cameras will photograph the rover's exact position . This routine, carried out each day until the rover stops working, could carry Sojourner up to 100m from the lander in 30 day's time.
The lander itself is equipped with a variety of instruments much more complex than those on Viking. Its camera mast stands one metre above the surface, almost a third higher than any camera on Viking, and will give a much better vantage point. Special filter packs for each camera will help to give clues about minerals present in the Martian soil.
Magnets attached to the lander will attract airborne, iron-rich dust. Photos of these magnetic patches will tell scientists about the size and composition of the dust particles.
The lander's two imagers will photograph the moon Phobos at night, showing controllers how much dust lies suspended in the Martian atmosphere. Special filters will allow cameras to look directly at the Sun to judge the sky's opacity.
At several times during the day the lander’s cameras will photograph wind socks placed on the meteorology mast at six different levels. This will give information about prevailing winds and air flow characteristics of the surrounding terrain. Heat sensors that read air temperature are placed at three different levels up the mast and at the top there is a sensor to measure wind direction. Whereas Viking just took measurements at one height, Pathfinder will give a three dimen-sional model of the atmosphere at the landing site.
Future Surveyor flights that will be launched every two years through to the year 2003 will combine the global views of an orbiter with regional close-ups provided by a lander/rover pair. Rover missions will explore the polar regions of Mars and ancient river beds. A future mission may return a sample of Martian rock as early as 2001.
If the Pathfinder mission is successful, the search for potential life will no longer be confined to one spot but will move over the most promising places on Mars.
by Sinead Quin
YOUR SIGNATURE OR MESSAGE IN SPACE!
As many of you will know, the joint ESA/ NASA mission Cassini/ Huygens is due to be launched in October of this
year. ESA is planning to fly a CD-ROM on board Huygens containing signatures and messages from thousands of
Europeans. Those members who attended the UKSEDS conference in November may have already added their
message, but anyone else wanting to contribute should do so via the special Internet site (http:// www.huygens.com).
If you do not have access to the internet, UKSEDS will be happy to accept your messages at the above postal address and enter them for you.
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UKSEDS 8TH NATIONAL STUDENT SPACE CONFERENCE
On the weekend of 16th-17th November last year, the University of Kent held the annual UKSEDS conference and Annual General Meeting. The highlight of the conference was undoubtedly the presentation given by Russian Cosmonaut Alexander Serebrov, who spoke about life in space, the early days of the Soviet space programme and international co-operation on the Mir and Alpha space stations.
Lectures were given by exhibitors the First Millennial Foundation about their Project and Aspire Space as well as other speakers, covering subjects from the Cassini/Huygens mission to Spaceplanes to Satellite Observations. The lecture about Mars given by Dr. Mark Burchell from the University of Kent coincided with the unfortunate demise of the Mars ‘96 mission but, as we are reminded by the article on the front of this newsletter, other missions to Mars have been planned and will hopefully meet with more success.
We were also joined by representatives from Surrey Satellite Technology Ltd. and Mare Crisium Space Consultants, who both gave interesting lectures, and Astrodome, an inflatable planetarium in which demonstrations were given throughout the conference.
The weekend was a highly informative and enjoyable one, as I am sure all who attended will agree.
NEWS ON THE 9TH UKSEDS CONFERENCE
If you missed the conference last year, be sure that you attend this year’s conference at the University of Leicester on 22nd-23rd November. Guest Speakers include Sir Patrick Moore and Prof. Heinz Wolff, with more to be announced in the future.
Could there be water on the Moon? Recent developments in the Clementine mission have indicated that there might be. Analysis of Clementine’s Bistatic Radar data has revealed the possibility of a permanent frozen water-ice lake in a crater near the south pole of the Moon.
Clementine was an application of Cold War technology, developed jointly by NASA and the Strategic Defence Initiative Organisation (once known as Star Wars). Its objective was deep space testing of military-developed sensors and spacecraft components, as well as to make a scientific study of the Moon and the asteroid 1620 Geographos. These observations were made at various wavelengths (UV, IR and laser ranging altimetry among others), for the purpose of assessing the surface mineralogy of the Moon and the asteroid, obtaining lunar altimetry from 60 degrees north to 60 degrees south latitude, and determining the size, shape, rotational characteristics, surface properties, and cratering statistics of Geographos.
Unfortunately, Clementine never got a chance to study Geographos as, after leaving lunar orbit, a malfunction in one of the on-board computers caused a thruster to fire until it had used up all of its fuel, leaving the spacecraft spinning at about 80 RPM with no spin control. However, the bistatic radar experiment of the Moon was conducted, and measured the magnitude and polarisation of the radar echo for selected lunar areas. Around the South polar regions, anomalous reflections of the radar signal were observed. Analysis shows that this is localised to the perman-ently shadowed regions of the lunar south pole. A probable explanation for these differences is the presence of ice.
This raises the question: Where could this ice have come from?
The most likely source is a comet. Several million years ago, a comet could have collided with the Moon. In the impact, its kinetic energy would have been converted to heat. Most of the ice would have evaporated, but some could have been scattered into the resulting crater. This ice would sublimate rapidly if it were illuminated by the Sun. However, in a permanently dark crater, the temperature remains low, which greatly reduces the rate of sublimation. It could conceivably remain there for many millions of years.
Lack of water, which is essential to support life, will be one of the main problems of any future base on the Moon. If there is indeed ice present on the Moon it makes a permanently manned Moon base a more realistic proposition. It would supply drinking water and also oxygen and fuel for spacecraft, by electrolysis. When electrolysed, water splits into hydrogen and oxygen, which are the two main components of rocket fuel. Spacecraft could conceivably travel from the Moon to Earth utilising Moon water. This may, however, be a waste of a valuable resource. One other possible alternative is to use powdered aluminium and lunar oxides.
There is a drawback to this proposed base, however. Astronomers have long wanted an observatory on the dark side of the Moon. The Moon’s mass would block out almost all of the light (and other electromagnetic) pollution from the Earth. Unfortunately, it would not be practical to build such an observatory on the same site as the proposed Moon base. One of the main purposes of Moon based observation would be to get data in the wavelengths which are absorbed by the Earth’s atmosphere, such as the infra red band absorbed by water vapour. But ice mining operations would create clouds of water vapour, which would be almost as bad as basing the telescopes on the Earth!
Despite this minor problem, if the presence of ice is confirmed, we will have moved a little closer to the conquest of the Moon...
by Alex King
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