Spaceflight Now: Delta launch report

A new Martian odyssey is about to begin

Posted: March 30, 2001

An artist's concept of Mars Odyssey at the Red Planet. Photo: NASA/JPL
With memories of recent back-to-back failures still painfully fresh, NASA is leaving no stone unturned to make sure the $305 million Mars Odyssey probe makes it safely into orbit around the Red Planet later this year.

The solar-powered 758-kilogram spacecraft is scheduled for launch April 7 from the Cape Canaveral Air Force Station atop a Boeing Delta 2 rocket. If all goes well, the Odyssey orbiter will slip into a highly elliptical orbit around Mars on October 24.

Over the next 76 days, the spacecraft will dip into the upper atmosphere of Mars some 273 times, using a complex -- and somewhat risky -- aerobraking procedure designed to put the Odyssey into a two-hour circular orbit at an altitude of about 400 kilometers.

Then the real work will begin: a full martian year of observations to map the mineralogy and chemical composition of Mars' frigid surface, to measure the planet's radiation environment and to assemble a medium-resolution photographic atlas of the entire world.

Given past failures, the stakes are high. But the NASA-industry team is confident of success.

"With any planetary mission like this, you get that range of emotions from excitement to nervousness," said Jeffrey Plaut, deputy project scientist of the Mars Odyssey mission at the Jet Propulsion Laboratory.

"At the program level ... maybe nervousness is the right word. Because nobody wants to see another failure," said Plaut. "However, at the level of the people who actually do the work, there's a high level of confidence that we're doing everything right."

Lessons learned
In September 1999, NASA's Mars Climate Orbiter crashed into the Red Planet because English units were used for critical reorientation rocket firings instead of metric units as required. It was one of NASA's most embarrassing blunders.

  Mars '98 missions
Artist's concept of the two Mars '98 missions: Climate Orbiter and Polar Lander. Photo: NASA/JPL
Three months later a companion spacecraft, the Mars Polar Lander, disappeared without a trace during descent to the surface. Engineers believe the lander's engines shut down too early because of an electrical glitch.

In the wake of the failures, NASA's Mars exploration program underwent a painful reassessment and restructuring.

"We went through and identified every parameter that could be critical to mission success and then went forward and did a verification of all these parameters both internally, within the team, and also with an outside group," Plaut said.

As a result, the kind of communications breakdown that lead to the Mars Climate Orbiter's demise "is very unlikely to crop up again," he said.

But getting into the proper orbit will not be easy. The aerobraking procedure must be completed within 90 days to ensure the Odyssey probe ends up in a polar orbit carrying it over the Earth-facing side of the planet at what amounts to mid afternoon local Mars time.

That will ensure proper lighting on Odyssey's large solar array and maximize the return from the spacecraft's suite of science instruments.

Odyssey is equipped with three sets of instruments: gamma-ray and neutron spectrometers; a radiation monitor; and a medium-resolution camera system capable of visible and infrared observations.

Illustration of Odyssey with description of its components. Photo: NASA/JPL
The neutron spectrometer will look for signs of ice in the martian soil while the gamma-ray spectrometer will measure the abundance of rock-forming elements like silicon, iron, magnesium, potassium, calcium and others.

"Unlike a camera, where you just take a picture and you can send it back that day and start analyzing it, the gamma-ray spectrometer suite of instruments needs to have a long period of observations before we get any real solid results," Plaut said.

"We want to be able to map the abundance of those elements in the upper 10 centimeters or so of the soil. But in order to do that we need to have a long-duration mission. We really need to be there for a good solid year, a full martian year."

Operating in its infrared mode, Odyssey's camera system will map the entire planet at 100-meter resolution. It will look for temperature differences on the planet's dark side that could mark the locations of active hydro-thermal systems below the surface.

"There has been this recent evidence of the possibly recent flow of water on the surface and if any of that activity is happening while we're there in orbit, we should be able to see it," Plaut said.

Working in visible light, Odyssey's camera will be able to produce a medium-resolution map of the planet at 18 meters per pixel. That translates into image swaths roughly 20 kilometers wide by 300 kilometers long.

"We'll wind up with thousands of postage stamps and we'll have to stitch them all together," Plaut said. "It would probably take an additional year of mapping operations to complete that map."

The goal is to characterize potential future sample return mission landing sites and to identify areas with deposits associated with earlier water activity.

Flight Data File
Vehicle: Delta 2 (7925)
Payload: 2001 Mars Odyssey
Launch date: April 7, 2001
Launch times: 11:02 a.m. EDT or 11:32 a.m. EDT
Launch site: SLC-17A, Cape Canaveral, Fla.