Orbital missions

Moore (1998) suggested that the data available could be interpreted in terms of an ice crust 10-15 km thick. Christopher Chyba from the SETI Institute (Mountain View, California) has published articles in Nature (2000), the Proceedings of the National Academy of Sciences (2001a) and in Science (2001b) in which he suggests that a detailed study of this Jovian moon is necessary he discusses the possibility of a complex ecosystem, nourished by the radiation coming from outer space, on or in the ice layers of the moon. The planned Europa orbiter mission may provide certainty on this, but at least another five years of uncertainty lie ahead. The use of a submersible robot to study the (possible) ocean layer and its floor has been discussed. 

The most recent research results show that it is difficult to detect formerly liquid water on Mars. Pictures of what are assumed to be seafloors and riverbeds are no longer considered to be certain evidence that flowing water was always present in all the regions of Mars. Critical examination of some landscapes indicates that they were carved by lava flows and not by water. Only in the case of the edges of craters, and some river gullies, does it appear quite clear that they were formed by liquid water. However, at the time of writing, the Mars Reconnaissance Orbiter mission is only a few weeks old, so further important results (and perhaps surprises) on the surface and mineralogy of Mars can be expected (Baker, 2007). 

In this chapter we summarize what we know about the chemical composition of Mercury, with emphasis on assessing the amount of FeO in the bulk planet. FeO is a particularly useful quantity to evaluate the extent to which Mercury is enriched in refractory elements, because its concentration increases with decreasing temperature in a cooling gas of solar composition (e.g., Goettel, 1988). We then examine models for the composition of Mercury and outline tests that future orbital missions to Mercury will be able to make. 

Ni-Hy batteries have been used in several Earth and planetary orbiting missions since the first commercial flight by INTELSAT V in 1983. Because of its demonstrated long life in GEO, this battery has been the workhorse for commercial communications satellites over the past 20 years. NASA first utilized Ni-H2 batteries in a LEO orbit when it launched the HST mission. These batteries, operating at a low 10 % DOD, have performed flawlessly since 1990. 

Power source Initial average power, W Spacecraft Mission type Launch date Orbital lifetime, yr... 

Now consider the hypothetical problem of trying to teach the physics of space flight during the period in time between the formulation of Kepler s laws and the publication of Newton s laws. Such a course would introduce Kepler s laws to explain why all spacecraft proceed on elliptical orbits around a nearby heavenly body with the center of mass of that heavenly body in one of the focal points. It would further introduce a second principle to describe course corrections, and define the orbital jump to go from one ellipse to another. It would present a table for each type of known spacecraft with the bum time for its rockets to go from one tabulated course to another reachable tabulated course. Students completing this course could run mission control, but they would be confused about what is going on during the orbital jump and how it follows from Kepler s laws. 

Until now, Mercury has only been studied more closely by one spacecraft (Mariner 10, 1974), since its nearness to the sun means that spacecraft approaching it are subject to particularly extreme conditions. NASA s MESSENGER (Mercury Surface, Space, Environment, Geochemistry and Ranging) was launched in 2004 and is planned to reach Mercury in March 2011, and then to orbit the planet. The main tasks of the MESSENGER mission are to map the planet, to make measurements of its magnetic field and to collect data relevant to its geological and tectonic history (Solomon, 2007). 

The fourth method, astronomical measurement, is (like the Doppler method) based on the observation and measurement of tiny motions of a star which are due to the mass(es) of the orbiting planet(s). A primary goal of the Space Interferometry Mission (SIM) is the discovery of planets similar to Earth, which orbit around stars like the sun. The SIM is due to start in 2009, and the measurements carried out will increase the accuracy of determinations of distances of stars in our galaxy several hundred times. Exact information can be found in the catalogue which forms part... 

The Darwin mission will not be carried out until the middle of the next decade. However, the COROT (Convection, Rotation and Planetary Transits) telescope was launched from the Baikonur cosmodrome in December 2006. The satellite, which weighs 630 kg, circles the Earth at a height of about 900 km in a polar orbit. The mission is planned to last 21/2 years, and more than 120,000 stars are to be observed. 

The start of NASA s Kepler mission is planned for February 2009 and has goals similar to those of the COROT project, though rather more ambitiousiit is intended to determine the percentage of terrestrial and larger planets there are in or near the habitable zone of a wide variety of stars, and also to determine the distribution of sizes and shapes of the orbits of these planets. 

Rosetta mission The mission to orbit and send a probe to land on the comet 67P/Chur-... 

Finally, and tantalizingly for this book and astrochemistry, there is Titan. The Cassini-Huygens mission is now in orbit in the Saturnian system as the book is published. The Huygens probe has already made the descent to the surface of Titan and the data have been transmitted back successfully. Scientists, astronomers, astrochemists and astribiologists are trying to understand it. I have taken a brief look at Titan as a case study to apply all that has been learnt and to review the possibilities for astrochemistry in what is surely to be a very exciting revelation of the structure and chemistry of Titan. 

On 23 September 1999 the Mars Climate Orbiter,one of the missions in a long-tenn program of Mars exploration, birned out completely. 

An example of propellant tailoring is the fuel used to launch the first U. S. satellite into orbit. The original fuel for the launch vehicle was ethyl alcohol. MAF-4 (also known as hydyne or U-DETA), a mixture of 60% UDMH and 40% diethylenetriamine (DETA), was formulated to simulate the physical properties of C2H5OH but provide the increased propellant performance (using liquid oxyen as the oxidizer) requirements of the mission. 

Polar Satellite Launch Vehicle (PSLV) For launching IRS/Sun-Synchronous Orbit (SSO) Satellites. India launched its first unmanned spacecraft under its mission Chandrayaan- to explore the moon on October 22, 2008 with the help of upgraded version of PSLV (also called PSLV-XL). 

Orbital geochemical analyses since the Apollo and Luna sample return missions have revolutionized our understanding of the composition of the crust and mantle. As an example,... 

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