February 22, 2017

ESA celebrates ExoMars orbiter success, keeps vigil for lost lander

Artist's concept of the ExoMars Trace Gas Orbiter firing its main engine to enter orbit around Mars. Credit: ESA/ATG medialab
Artist’s concept of the ExoMars Trace Gas Orbiter firing its main engine to enter orbit around Mars. Credit: ESA/ATG medialab

A European-built orbiter designed to seek out the source of methane on Mars slipped into orbit around the red planet Wednesday after a seven-month interplanetary journey, but mission control lost contact with an experimental landing probe just before touchdown.

Both spacecraft — part of the joint European-Russian ExoMars program — reached Mars around the same time Wednesday for simultaneous maneuvers to swing into orbit and plunge into the red planet’s atmosphere.

The Schiaparelli lander, shaped like a flying saucer with a diameter of nearly 8 feet (2.4 meters), dived into the Martian atmosphere as expected around 1442 GMT (10:42 a.m. EDT) Wednesday.

Designed for a technology demonstration mission, Schiaparelli had heat shield tiles, a parachute and nine rocket thrusters to slow its speed from 13,000 mph (21,000 kilometers per hour) to zero in less than six minutes.

But something went wrong in the last phase of the descent, interrupting a real-time beacon signal sent back to Earth to a vast radio telescope array in Pune, India. The carrier tone went silent after mission controllers reported Schiaparelli’s supersonic parachute had deployed, but the signal only told engineers whether the spacecraft was transmitting, and did not contain telemetry data that might reveal the root of the problem.

European Space Agency officials waited to receive a recording of Schiaparelli’s beacon signal from the Mars Express orbiter around the red planet to confirm some sort of glitch with the Indian antennas was not responsible for the loss of communications.

“We saw the signal through the atmospheric phase — the descent phase. At a certain point, it stopped,” said Paolo Ferri, head of ESA’s mission operations department. “This was unexpected, but we couldn’t conclude anything from that because this very weak signal picked up on the ground was coming from an experimental tool.”

The telescope array in India was never designed to communicate with deep space missions like Schiaparelli, but engineers added equipment to the antenna network — the largest in the world — for Wednesday’s Mars landing in hopes of gaining real-time insight into the status of the mission.

Otherwise, ground controllers would have had to wait for Mars Express for news on the 1,272-pound (577-kilogram) landing craft.

This graphic illustrates Schiaparelli's landing sequence. Credit: ESA
This graphic illustrates Schiaparelli’s landing sequence. Credit: ESA

It turns out the ground team at the European Space Operations Center in Darmstadt, Germany, had to wait all day Wednesday as data on Schiaparelli’s landing trickled back to Earth and hopes for the mission’s successful landing waned.

The carrier signal from Schiaparelli relayed by Mars Express also abruptly ended shortly before landing, just as the beacon tone received in India.

“The Mars Express measurement came … and confirmed exactly the same: the signal went through the majority of the descent phase, and it stopped at a certain point that we reckon was before the landing,” Ferri said.

“There could be many many reasons for that,” Ferri said. “It’s clear these are not good signs, but we will need more information.”

The newly-arrived Trace Gas Orbiter, Schiaparelli’s mothership, recorded detailed telemetry broadcast by the lander — not just the beacon signal — and that data should be beamed back to Earth overnight, according to Ferri.

“This is fundamental because we should remember that this landing was a test, and as part of the test, you want to know what happened,” Ferri said.

“If the landing were to fail, presumably from TGO we will know what was the last thing that worked all right,” said Jorge Vago, ESA’s ExoMars project scientist, in an interview with Spaceflight Now on Tuesday, before Schiaparelli’s landing attempt.

Officials hope to share more on what they know about Schiaparelli’s fate in a press conference Thursday at 0800 GMT (4 a.m. EDT).

ESA Exomars 2016
Artist’s concept of the Schiaparelli lander during descent. Credit: ESA/ATG medialab

Schiaparelli rode to Mars piggyback on the Trace Gas Orbiter after their tandem launch March 14 aboard a Russian Proton rocket, then separated Sunday for the final approach to the planet.

Both ExoMars spacecraft were manufactured by an industrial team led by Thales Alenia Space.

The orbiter fired its main engine at 1305 GMT (9:05 a.m. EDT), smoothly slowing the craft’s velocity by more than 3,300 mph (1.5 kilometers per second) during a 139-minute burn.

The final few minutes of the make-or-break rocket maneuver occurred as the spacecraft flew behind Mars, temporarily cutting off communications. When mission control regained contact with the Trace Gas Orbiter, telemetry showed the probe was healthy and had completed the orbit insertion burn as planned.

The confirmation sparked a round of applause inside the ExoMars control center, but attention quickly turned back to Schiaparelli.

“Part of the mission is a clear go,” said Don McCoy, ESA’s ExoMars project manager, after the Trace Gas Orbiter braked into orbit around Mars without difficulty. “For the lander, we have received some data … We’ve seen a series of indicators of the entry, parachute deployment, release of the backshell, etc. We don’t have the full set of data.”

The orbiter is the primary part of the mission, carrying four science instruments to take pictures, locate water resources, and search for the sources of intermittent methane detected in the Martian atmosphere, an indicator of ongoing biological or geological activity.

ESA expects the Trace Gas Orbiter to function through at least 2022 and help relay commands and science data between Earth and a fleet of existing and planned rovers on the Martian surface.

NASA provided two radio packages for the orbiter to link up with the Curiosity and Opportunity rovers, along with planned rovers from NASA and ESA scheduled for launch in 2020.

Officials billed Schiaparelli as a technology demonstrator, and the probe was aiming to become the first European spacecraft to successfully land and function on Mars.

Engineers hoped lessons learned from Schiaparelli will feed into the design of the second part of the two-launch ExoMars program, a European-built rover scheduled for liftoff in mid-2020.

Under the terms of their partnership with ESA, Russian engineers will design and build the descent module for the ExoMars rover, but the computer and parts of the lander’s guidance system will come from Europe. Schiaparelli was supposed to verify parts of the design worked at Mars.

A doppler radar altimeter was supposed to activate when Schiaparelli jettisoned its forward heat shield under parachute and collect data on the spacecraft’s altitude and speed. The measurements were to go to Schiaparelli on-board computer to control the thrust of nine hydrazine-fueled rocket engines fixed around the perimeter of the probe.

The thrusters were programmed to cut off around 6 feet, or 2 meters, above the Martian surface, and Schiaparelli was to fall to the ground cushioned by a crushable carbon-fiber crash structure.

A downward-facing descent camera was expected to take images during the last phase of Schiaparelli’s descent, and the lander’s computer was supposed to switch on a weather station after touchdown to monitor the temperature, humidity, pressure, dust opacity, wind speed, and wind direction at site landing site in Meridiani Planum, a relatively flat plain near the Martian equator.

Named for Italian astronomer Giovanni Schiaparelli, the lander was to become the first mission to land on Mars during the planet’s global dust storm season. One of the sensors aboard the craft was designed to measure electrical fields in the Martian atmosphere, one of the mechanisms scientists think might drive dust storms.

“The Schiaparelli lander was designed to be able to land in a global dust storm, a big one where you don’t see anything,” Vago said. “From the point-of-view of hypersonic entry, heat shield performance, and parachute performance, it should all be OK.”

The lander, primarily funded and built in Italy, was also fitted with instrumentation to track the density, pressure and temperature of the atmosphere from the point of entry at an altitude of 80 miles (130 kilometers) to the surface. Another payload on Schiaparelli was a compact array of laser retroreflectors to help future orbiters precisely locate the lander.

Schiaparelli only carried batteries to power its science sensors, computer and radio transmitter, so engineers expected it to shut down within a few days of landing.

ESA said ground controllers will have multiple opportunities in the comings to attempt to contact Schiaparelli — assuming it is safely on the surface — before its batteries run down.

“We don’t know all the details (about Schiaparelli’s status), but this is typical for a test,” said Jan Woerner, ESA’s director general. “We did this in order to get data about how to land European technology on Mars, therefore, all the data we will get tonight … will be used to understand how to manage the next landing when we will go with a European rover.”

Wednesday’s nail-biting landing attempt came 13 years after the Beagle 2 probe built in Britain reached the red planet.

Mission control never heard from Beagle 2 after its landing attempt, but scientists last year revealed new imagery from Mars orbit apparently showing the lander sitting the surface with its power-generating solar arrays still partially folded.

The discovery led engineers to conclude Beagle 2 may have survived its landing, but a problem prevented full deployment of the solar panels, potentially blocking the antenna that was to radio its status to Earth.

Schiaparelli’s flight to Mars was Europe’s second try, with a much bigger package than Beagle 2. It went to Mars with the new doppler radar guidance system, modernized control algorithms and a computer that will be crucial to the 2020 mission’s rover landing.

The ExoMars Trace Gas Orbiter is ESA’s second spacecraft circling the red planet after Mars Express, which is still flying well beyond its design life after arriving at Mars in 2003.

With the insertion of the latest orbiter, there are now six active satellites around Mars, including the two ESA science stations, three NASA orbiters, and an Indian spacecraft.

Navigators intended for the Trace Gas Orbiter to enter into an initial egg-shaped orbit taking the spacecraft as close as 186 miles (300 kilometers) and as far as 60,000 miles (96,000 kilometers) from Mars.

Experts verified the orbiter was right on course after its orbit insertion burn.

“Yes, the TGO is captured in orbit around Mars, and yes, it’s in a very nominal orbit of four days duration, only a couple hours more, but this is within a few percent, and it’s perfectly normal,” said Michel Denis, ExoMars flight director.

All systems on the orbiter are performing well, he said.

“It’s all good,” Denis said. “It’s a good spacecraft at the right place, and we have a mission around Mars, another one.”

The orbiter will turn on its camera and science instruments for two orbits — about eight days — in November for a first look at the red planet since arriving, according to Vago.

“We will turn the instruments on and hope to be able to make some interesting first observations then,” Vago said. “Don’t expect any magnificent revelations on the distribution of methane or trace gases just in two orbits, but some images for sure and the confirmation that the instruments work as well.”

Starting in January, the orbiter will begin an aerobraking campaign, dipping into the upper fringes of Mars’ atmosphere on each lap around the planet. Drag on the spacecraft’s solar panels will gradually lower its altitude, with the satellite ending up in a circular 250-mile-high (400 kilometer) orbit by early 2018.

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.