Now eight days past launch, Mars Climate Orbiter is performing well under the control of its first "housekeeping" sequence, which was successfully transmitted to the spacecraft and activated yesterday. Deep Space Network (DSN) coverage of the spacecraft has dropped to three contact periods per day of roughly four hours each. This level of coverage will continue out through Jan. 11, 1999 (L+30 days).
This morning commands were successfully transmitted to the spacecraft to complete the configuring of its software system for early cruise. The orbiter's autopilot is now programmed to track the Earth with its medium-gain antenna. The vehicle's orientation will evolve slowly as the Earth and spacecraft follow their respective orbits around the sun. Analysis of the spacecraft's power and thermal control subsystems indicate that it can operate safely in this manner for at least one month, and probably longer, allowing sufficient time for the flight team to conduct the initial Mars Polar Lander post-launch operations before returning to long-range planning for the orbiter.
Preparations are nearing completion for the orbiter's first Trajectory Correction Maneuver (TCM), designated TCM-1. Testing and verification of the maneuver commands will be completed later today, with the maneuver scheduled to begin at 1:30 P.M. PST on Monday, Dec. 21st.
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
After a one-day delay, NASA's Mars Climate Orbiter blasted off launch pad 17A at Cape Canaveral Air Station, FL, at 1:45 p.m. Eastern Standard Time today and hurtled skyward on a 9-1/2- month flight to Mars to embark on a study of the planet's climate and current water resources. The 24-hour launch delay will not change the spacecraft's arrival date at Mars on September 23, 1999, or alter its primary mapping mission.
The spacecraft shot through a breezy, cloud-laced mid- afternoon sky atop a Delta II launch vehicle on the second day of the primary launch period with new onboard software to guard against overcharging the spacecraft's battery. The orbiter team tested the new software using the Mars Polar Lander spacecraft at Kennedy Space Center, FL, as a testbed. Mars Polar Lander, which will join Mars Climate Orbiter at Mars in December 1999, is currently being processed for launch on January 3, 1999.
Sixty seconds after liftoff, the four solid-rocket boosters were jettisoned, two at a time, followed by first-stage separation and second-stage engine ignition. The second-stage burn lasted approximately 11 minutes, 22 seconds, placing the spacecraft in a low-Earth orbit at about 189 kilometers (117 miles) above Earth's surface.
Third-stage separation occurred at approximately 2:26 p.m. EST, followed by a burn of the third-stage engine for 88 seconds. Once out of Earth's gravitational grasp, the orbiter was jettisoned from the third stage using the spacecraft's onboard thrusters to remove all remaining motion. Four minutes later, the spacecraft's solar arrays were unfolded and pointed toward the Sun for power. NASA's Deep Space Network complex near Canberra, Australia, acquired the orbiter's signal at 2:45 p.m. EST. Spacecraft controllers at Lockheed Martin Astronautics in Denver, CO, and at the Jet Propulsion Laboratory in Pasadena, CA, are now assessing the spacecraft's initial performance.
Now on its way to Mars, the Climate Orbiter will rely on its low-gain and medium-gain antennas for communications with Earth during the first half of the journey to Mars. Ground-controllers will track the spacecraft 24 hours a day during the first week of cruise, then reduce tracking time to 12 hours a day using 34- meter (112-foot) antennas of the Deep Space Network. Twelve days into flight, one of the spacecraft's science instruments, the Pressure Modulator Infrared Radiometer, will be powered on and acclimated to the environment of space.
The first trajectory correction maneuver to remove errors in the spacecraft's flight path introduced at the time of launch will be performed 10 days into the cruise phase, on December 21, 1998. That thruster firing will be the largest and longest of all four trajectory correction maneuvers, lasting about 15 to 20 minutes and changing the spacecraft's velocity by about 30 meters per second (67 miles per hour).
Mars Climate Orbiter and Mars Polar Lander are the second set of spacecraft to be launched in NASA's long-term program of robotic exploration of Mars.
ROYAL ASTRONOMICAL SOCIETY
2 December 1998
'Mars Climate Orbiter is particularly significant since it will be the first mission to Mars with a substantial British component,' said Professor Fred Taylor of Oxford University's Department of Atmospheric, Oceanic and Planetary Physics.
The 44kg instrument, named PMIRR (Pressure Modulator Infrared Radiometer) represents the culmination of more than ten years of effort aimed at understanding the climate on Mars. A similar PMIRR instrument carried on a previous NASA spacecraft known as Mars Observer was lost when the spacecraft failed to respond to transmissions after it attempted to enter Mars orbit in 1993.
Many of the Mars Observer instruments were rebuilt and flown on the first Mars Surveyor but PMIRR had to wait because it was too large to be included. The new instrument has been designed and built as a collaboration between NASA's Jet Propulsion Laboratory (JPL) in California and the Department of Atmospheric, Oceanic and Planetary Physics at Oxford University. Its design is based closely upon a successful series of instruments developed by Oxford University for remote sensing the Earth's atmosphere which have flown on several NASA spacecraft since the early 1970's.
'We're looking to find out how the atmosphere works, how it contributes toconditions on the surface and how the climate may have changed in the past,' said Professor Taylor.
Although there are a number of similarities between the way the atmosphere behaves on Earth and Mars, the thin Martian atmosphere still holds a number of mysteries. Despite a surface pressure on Mars which is only about 1% of that on Earth, the carbon dioxide-rich atmosphere is nevertheless very active. Almost a quarter of the carbon dioxide seems to condense onto the polar ice caps during winter.
No liquid water can exist on Mars today, but water is transported in the atmosphere. By studying how the amount of water varies with altitude and latitude (distance from the equator) during the year it is hoped to obtain clues about the location of other, hidden, water reservoirs, such as subsurface permafrost.
The third extremely significant component of the atmosphere is dust, which has a considerable impact on the temperature of the atmosphere and surface. The amount varies from season to season, and occasionally global dust storms completely obscure the planet during the southern hemisphere's summer.
Starting with the 1999 Mars Polar Lander, many of the missions planned for Mars exploration over the next decade involve surface landers. While meteorological stations on the surface give extremely valuable measurements of local weather and near surface effects, the global view obtained by PMIRR will enable scientists to put this data into a planetary context.
The PMIRR data will eventually lead to more accurate global models of the Martian environment, a necessary precursor for future robotic and human exploration missions.
By measuring the infrared (heat) radiation coming from the planet after it passes through the gas in the modulator, a signal is produced which is specific to the gas chosen. This is particularly useful when remote sensing Mars because the infrared radiation from the gases is mixed with radiation from the dust which always seems to be present in the atmosphere.
All of the 9 infrared detectors used in PMIRR were supplied by GEC-Marconi Infrared in Southampton. These were assembled into working optical units in Oxford and delivered to NASA/JPL for installation into the instrument. Almost all of the 52 lenses, filters and other optics used in PMIRR were supplied by Reading University Infrared Multilayer Laboratory. The only exceptions are two innovative "mesh" filters used at long infrared wavelengths which were developed and built by Queen Mary and Westfield College, London.
Notes:
The Mars Climate Orbiter is due for launch on Dec. 10 on a Boeing Delta 2 launch vehicle from Cape Canaveral Air Station, Florida. The orbiter will arrive at the Red Planet in September 1999 and will circle Mars for a whole Martian year (about 2 Earth years) to study the atmosphere and climate. Apart from PMIRR, the only science payload on board is a 4kg colour imager comprising two tiny cameras.
The Mars Polar Lander is scheduled for launch on Jan. 3 1999. It will touch down near the planet's South Pole on Dec. 3, 1999. Riding aboard the cruise stage of the lander are two microprobes developed by NASA's New Millennium program, under the name Deep Space 2. The microprobes will be released just before atmospheric entry, and then will crash into the Martian surface near the landing site to test 10 advanced technologies and search for traces of subsurface water ice.
More details of the Mars Climate Observer and Mars Polar Lander missions can be found on the Internet at the following home pages:
The UK contribution to PMIRR was funded by the Particle Physics and Astronomy Research Council (PPARC).
Kennedy Space Center
Sept. 11, 1998
When it first arrives at the red planet, the Mars Climate Orbiter will be used primarily to support its companion Mars Polar Lander spacecraft, planned for launch on Jan. 3, 1999. After that, the Mars Climate Orbiter's instruments will monitor the Martian atmosphere and image the planet's surface on a daily basis for one Martian year, the equivalent of two Earth years. During this time, the spacecraft will observe the appearance and movement of atmospheric dust and water vapor, as well as characterize seasonal changes on the surface. The detailed images of the surface features will provide important clues to the planet's early climate history and give scientists more information about possible liquid water reserves beneath the surface.
The spacecraft is to be readied for launch in NASA's Spacecraft Assembly and Encapsulation Facility-2 (SAEF-2) located in the KSC Industrial Area. Among the processing activities to be performed in this clean room facility are a functional test of the science instruments and the basic spacecraft subsystems.
Checks of the communications system will be performed including a verification of the spacecraft's ability to send data via the tracking stations of the Deep Space Network to the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. and the Lockheed Martin plant in Denver, Colo.
Following these checks, the spacecraft will be fueled with the spacecraft bipropellants of hydrazine and nitrogen tetroxide and mated to a Star 48 solid propellant upper stage booster. Finally, the combined spacecraft and upper stage elements will undergo spin balance testing.
Meanwhile, at Launch Complex 17, the Delta II rocket will be undergoing erection and prelaunch checkout by Boeing on Pad A. The first stage is scheduled to be installed into the launcher on Oct. 29. Four solid rocket boosters will be attached around the base of the first stage on Nov. 2. The second stage will be mated atop the first stage on Nov. 4, and the fairing will be hoisted into the clean room of the pad's mobile service tower Nov. 6.
The Mars Climate Orbiter with its upper stage booster will be transported to Complex 17 on Nov. 30 for hoisting atop the Delta and mating to the second stage. After the spacecraft undergoes a state of health check the next day, the two halves of the fairing will be placed around it on Dec. 3. Finally, there will be a mission dress rehearsal.
At liftoff, the spacecraft will weigh 1,418 pounds (3,120 kilograms). It is 7.6 feet (25 meters) high, 6.4 feet (21 meters) deep, and 5.4 feet (18 meters) wide. Power is provided by a single large solar array which is 18.6 feet (61 meters) long and 6.8 feet (22 meters) across. After cruising in space for 286 days, the spacecraft will be captured in an elliptical orbit around Mars.
The eight-day primary launch period to achieve an optimum cruise phase and Mars planetary encounter begins with an instantaneous launch window at 1:56 p.m. EST, Dec. 10. There are two instantaneous windows each day. A secondary six-day period of launch opportunity begins Dec. 18. The last day available for launch is Dec. 25.
The 1998 Mars Climate Orbiter and Mars Polar Lander missions are managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, Calif. Lockheed Martin Astronautics, Denver, Colo. which built and operates the spacecraft, is JPL's industrial partner in the mission.
Back to ASTRONET's home page
Terug naar ASTRONET's home page