Tim Furniss/LONDON
The success of the Mars Pathfinder mission and of its Sojourner rover have generated huge public interest, especially in the perennial subject of manned flights to Mars. On the back of that success Daniel Goldin, NASA's Administrator, has challenged his scientists and engineers to come up with a proposal for a manned Mars flight which would cost just $25 billion, the price of ten Northrop Grumman B-2 bombers.
The major impetus for such a programme will be unlikely to materialise until a bit of Mars rock is returned from the surface of the planet - possibly in 2006 - and shows evidence that life once existed there. The hyped-up "Mars meteorite" rock has proved nothing other than being a potential damp squib.
Many Mars missions will have to be staged, however, even before such an unmanned sample return mission can be launched. Unless rapid advances in technology can be made, human flights are unlikely for at least another 20 years, despite NASA's high hopes (see box).
The US space agency's Johnson Space Center has, however, already proposed a 2.5-year mission which would involve astronauts staying on the Martian surface for 18 months, using the atmosphere there to produce fuel and oxygen. First support missions could begin in 2007, with the launch of unmanned components, followed by manned missions starting in 2009, leading to the establishment of the permanent base in 2016. A lot will depend on an already planned series of unmanned precursors.
MARS GLOBAL SURVEYOR
(MGS)
En route, arrival September 1997
Launched a month before the Mars Pathfinder, in November 1996, this spacecraft will operate from a polar orbit providing global maps and data on the distribution of minerals and will monitor the planet's magnetic field.
The 1,050kg craft will enter a preliminary orbit in September using a retro-rocket burn, and aerobraking manoeuvres will then bring it to its prescribed 93¹-inclination, Sun-synchronous, 367km circular orbit by January 1998.
Aerobraking was demonstrated during the final days of the Magellan Venus orbiter. The MGS will dip repeatedly into the top of the atmosphere at perigee. Atmospheric drag will cause a reduction in speed and orbit altitude, saving on the amount of on-board propellant.
The low-cost MGS will carry some of the experiments that were to have been operated in Martian orbit in 1993 from the Mars Observer, which was lost as it was preparing to enter orbit in August 1993.
The demise of this large, $800 million, spacecraft sparked off NASA's building of its "faster, smaller, better, cheaper," series of spacecraft. The MGS carries a magnetometer, electron reflectometer, laser altimeter, orbital camera, thermal-emission spectrometer, relay-radio system and radio-science instrument.
NASA hopes that the MGS will provide primary data until January 2000, after which it will become a data relay orbiter for future missions.
MARS SURVEYOR MISSION 1
Mars Surveyor Lander
Launch December 1998/Delta 2
Reaches target December 1999-January 2000
This 250kg, Lockheed Martin-built craft will be the first to visit one of the poles (south) of Mars, where it is expected to settle on alternate layers of clean and dust-laden ice. "These areas probably hold the key to understanding what appear to be quasi-periodic climate fluctuations on the planet," says Dr Wesley Huntress, NASA's Associate Administrator for space science.
The nature of the orbit of Mars in relation to the Earth during this launch window makes the mission the only one which can reach the poles during the next decade.
A part of the payload is a mast-mounted meteorological package with sensors to record atmospheric pressure, temperature and winds. A mast-mounted imager will take stereo images of the landscape and a 2m-long robot arm will be used pass surface samples to the on-board Thermal and Evolved Gas Analyser, to determine their content of ice and carbon dioxide.
The robot arm is part of NASA's New Millennium initiative to validate the technology of hardware for future missions. Another New Millennium project involves the impact of two 1.2kg, 103mm-long microprobes despatched from the Mars Surveyor Lander at cruise stage before Martian orbit entry.
These will fly the Deep Space 2 mission, to demonstrate key technologies which will enable network science and in situ and subsurface science data-acquisition analysis.
Russia will provide a laser radar, which measures atmospheric haze and dust. The lander also includes a camera built by Malin Space Science, San Diego, which will take wide-angle images of the landing area from 10s after its parachute has been deployed, at about 8km altitude, until its conventional rocket-assisted landing at a site which will be selected from high-resolution images from the MGS.
Mars Surveyor Orbiter
Launch January 1999/Delta 2
Reaches target September 1999
Also built by Lockheed Martin, the 450kg orbiter will carry a suite of instruments, including a 1kg advanced optical camera from Malin. The wide-angle camera will acquire daily weather maps with a resolution down to 1km, while a 40m-resolution medium-angle camera will study alterations on the surface caused by changes in atmospheric conditions and winds.
The orbiter will also carry an atmospheric instrument called the Pressure Modulator Infrared Radiometer to measure temperature profiles of the atmosphere and monitor its water vapour and dust content. The craft will use MGS-type aerobraking manoeuvres to enter its 350km circular orbit.
MARS SURVEYOR MISSION 2
Mars Surveyor Lander
Launch April 2001/Medlite
Arrives January 2002
This spacecraft will carry a high-profile experiment to demonstrate the possibility of manufacturing rocket propellant and oxygen using gases in the Martian atmosphere. This will be part of the unique joint work between the space-science and human-exploration sections in NASA, with a view to preparing the technology for eventual manned missions to Mars.
The lander's Mars In-Situ Propellant Production Precursor consists of six experiments. Three will: attempt to produce oxygen from carbon dioxide in the Martian atmosphere, using a heating plate; remove carbon dioxide from the atmosphere using a material called zeolite and then heat it to make carbon; and combine the carbon dioxide with hydrogen to produce methane for use as a rocket fuel. Other experiments will test equipment for a sample-return mission, including advanced solar cells, dust filtration, and heating and cooling systems.
The lander will also incorporate a small, advanced-technology rover capable of travelling over 10km (6 miles) across the Martian highlands during a year-long expedition. The rover will collect 3kg of soil samples for possible later return to Earth by a future robotic mission.
Other equipment on the lander will investigate the planet's soil properties and surface-radiation environment. "Before we can send humans into deep space, we need to understand the nature of the space environment and its effect on living systems," says Arnauld Nicogossian, acting Associate Administrator for life and micirogravity sciences at NASA.
Analysis of the dust and soil will also be necessary to understand any possible corrosive interactions with the systems planned to supply the habitation and working environment for future human explorers. The affect of Martian dust on solar panels will be an important element. Communications signals from the lander will be assessed for suitability for guiding a future spacecraft to a precise location nearby, to collect the samples. Total cost of the lander and orbiter missions is $311 million.
Mars Surveyor Orbiter
Launch March 2001/Medlite
Arrives December 2001
This orbiter will be the first to use the atmosphere of Mars to slow down and directly capture the spacecraft into orbit, in a technique called aerocapture. The science objectives of the mission are to conduct mineralogical mapping of the entire surface and characterise its orbital radiation environment in preparation for manned flights.
The radiation experiment is similar to the one carried aboard the fated Russian Mars probe which was lost soon after launch in November 1996. The 2001 orbiter also will provide data relay for the sister lander - and a possible Russian robotic rover mission.
MARS SURVEYOR MISSION 3
Mars Surveyor Orbiter
Launch March 2003/Medlite
Mars Surveyor lander
Launch March 2003/Medlite
MARS SURVEYOR MISSION 4
2005
Possible Mars sample-return mission, with rocks from 2001 Rover.
POSSIBLE MANNED
EXPEDITION
2007
Unmanned launches of Earth-return vehicle into Mars orbit, Martian surface lander, ascent vehicle and propellant-production module.
2009
Duplicate flights of 2007 equipment, and first crew, with surface habitat/laboratory modules.
2012 ,2014 and 2016
Steps toward building permanent Mars base.
Source: Flight International
