NASA’s Mars Odyssey Orbiter Captures Massive Volcano, Approaches 100,000 Orbits

NASA’s longest-lived Mars robot is about to reach a new milestone on June 30: 100,000 trips around the Red Planet since its launch 23 years ago. During that time, the 2001 Mars Odyssey orbiter has mapped minerals and ice on the Martian surface, identified landing sites for future missions and relayed data from NASA’s rovers and landers to Earth.

Scientists recently used the orbiter’s camera to capture a stunning new photo of Olympus Mons, the tallest volcano in the solar system. The image is part of an ongoing effort by the Odyssey team to provide high-altitude views of the planet’s horizon. (The first such view will be released in late 2023.) Similar to the perspective Earth astronauts will get when they board the International Space Station, this view will allow scientists to learn more about the clouds and dust in the Martian sky.

The most recent horizon photo, taken on March 11, captures Olympus Mons in all its glory. With a base stretching 373 miles (600 kilometers), the shield volcano rises to a height of 17 miles (27 kilometers).

“Normally we see Olympus Mons in narrow strips from above, but by turning the spacecraft toward the horizon we can see just how big it is above the landscape in a single image,” said Odyssey project scientist Jeffrey Plaut of NASA’s Jet Propulsion Laboratory in South Africa, California, which manages the mission. “The view is not only spectacular, it also provides us with unique science data.”

In addition to providing a still view of clouds and dust, such images, when taken over many seasons, can give scientists a more detailed look at the Martian atmosphere.

A bluish-white band at the bottom of the atmosphere indicates how much dust was present at this location during early fall, a period when dust storms typically rise. The purple layer above was likely due to a mixture of the planet’s red dust with some bluish water ice clouds. Finally, a blue-green layer can be seen at the top of the image, where water ice clouds extend about 50 kilometers into the sky.

How they took the photo

Named after Arthur C. Clarke’s classic science fiction novel “2001: A Space Odyssey,” the orbiter captured the scene with a heat-sensitive camera called the Thermal Emission Imaging System, or THEMIS, which Arizona State University in Tempe built and operates. But because the camera is intended to look at the surface, taking a horizon shot requires extra planning.

By firing thrusters positioned around the spacecraft, Odyssey can point THEMIS at different parts of the surface or even roll over slowly to view Mars’ small moons, Phobos and Deimos.

The recent horizon image was conceived many years ago as an experiment during the landings of NASA’s Phoenix mission in 2008 and Curiosity rover in 2012. As with other landings on Mars before and after those missions, Odyssey played a key role in relaying data as the spacecraft blasted toward the surface.

In order to beam their vital engineering data back to Earth, Odyssey’s antenna had to be aimed at the newly arrived spacecraft and their landing ellipses. Scientists were intrigued to learn that positioning Odyssey’s antenna for the task meant that THEMIS would be aimed at the planet’s horizon.

“We decided to just turn on the camera and see what it looked like,” said Odyssey’s mission operations spacecraft engineer, Steve Sanders of Lockheed Martin Space in Denver. Lockheed Martin built Odyssey and helps run day-to-day operations with mission managers at JPL. “Based on those experiments, we designed a sequence that keeps THEMIS’s field of view centered on the horizon as we go around the planet.”

The secret of a long space journey

What is the secret of Odyssey that makes it the longest continuously active mission to orbit a planet other than Earth?

“Physics does a lot of the hard work for us,” Sanders said. “But it’s the subtleties that we have to master again and again.”

These variables include fuel, solar energy and temperature. To ensure that Odyssey uses its fuel (hydrazine gas) sparingly, engineers must calculate how much is left, since the spacecraft does not have a fuel gauge. Odyssey relies on solar energy to run its instruments and electronics. This force varies as the spacecraft disappears behind Mars for about 15 minutes per orbit. And temperatures must remain balanced for all of Odyssey’s instruments to function properly.

“It takes careful monitoring to keep a mission going for so long while maintaining a historical timeline of scientific planning and execution, and innovative engineering practices,” said Odyssey’s project manager, Joseph Hunt of JPL. “We look forward to collecting more great science in the years to come.”