Twin NASA Probes Fire Engines Near Earth in a First for Mars Missions

NASA's twin ESCAPADE spacecraft have each completed an engine burn close to Earth that is meant to send them on to Mars, Space.com reported. The first probe did it on Nov. 7 and the second followed on Nov. 9, and NASA says both maneuvers went perfectly.

The agency says it is the first time it has used a powered Earth flyby to push a spacecraft toward Mars. If no problems arise, the pair will arrive at the Red Planet in September 2027.

The ESCAPADE flyby by the numbers

• Nov. 7 and Nov. 9: the dates of the two burns, one for each spacecraft, two days apart. Asal Naseri, acting associate flight director for NASA's Heliophysics Division, said the team had done the maneuver twice without a flaw.
• 26 months: how often Earth and Mars line up well enough for a standard launch to Mars. ESCAPADE was meant to leave in October 2024, but delays with Blue Origin's New Glenn rocket made it miss that window.
• November 2025: when the probes finally launched, on the second flight of New Glenn. Rather than wait for the next window, mission planners sent them on a looping, bean-shaped path that brought them back to Earth in early November 2026.
• About 10 days: how long the two craft spent passing through the long tail of Earth's magnetic field at a distance of some 1.19 million miles (1.91 million km) from the planet.
• 800,000 miles (1.27 million kilometers): roughly how far from Earth earlier missions had studied that tail. Beyond that distance it had been a mystery.
• September 2027: the planned arrival at Mars after a few minor course corrections.

What is behind the numbers

NASA's Mars missions have traditionally left Earth during a short launch window. ESCAPADE took a different route after missing its slot. Instead of sitting on the ground, the probes were parked in a looping orbit and brought back to Earth for a second chance to head out.

That return trip came with a hurdle. Each spacecraft had to fire its engines inside Earth's gravity well, according to Space.com. The move resembles the slingshot flybys spacecraft often use to change course, except that here the engine burn amplified the effect of the gravity assist instead of leaving the planet to do all the work.

Rob Lillis, the mission's principal investigator and a planetary and space physicist at the University of California, Berkeley, said, “No NASA mission has ever done this before.” He added that for most missions the approach is not needed.

Why it matters for science

The detour was not just a delay. Each probe is about the size of two refrigerators and carries three scientific instruments and a couple of cameras, all built to study Mars' unusual magnetic field. That field comes partly from charged particles streaming from the sun interacting with the planet's atmosphere, and partly from patches of strongly magnetic crust.

While looping around, the two craft also made measurements of Earth's magnetic tail, which the solar wind stretches out on the side facing away from the sun. Lillis said the data captured how that distant tail moves, flaps and carries plasma, and he described it as unprecedented. He said it was the first time two spacecraft had measured it at the same time.

A second chance came over the summer, when the probes were much closer to Earth and the moon was also crossing the magnetic structure. The ESCAPADE pair worked with the twin ARTEMIS-THEMIS spacecraft at the moon, giving scientists four viewpoints on the tail at once. Lillis said this kind of structure cannot generally be measured from afar, so spacecraft have to be there.

What happens next

After a few minor course corrections, ESCAPADE is expected to cruise to Mars and arrive in September 2027. Once there, the pair will turn their instruments on the planet's magnetic environment, the job they were designed for.

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Around Prague, based on reporting by Space.com