After a seven month cruise between worlds, ESA and Russia’s Trace Gas Orbiter (TGO) and the Italian Space Agency’s Schiaparelli lander arrived for their crucial orbit insertion burn (TGO) and landing (Schiaparelli) on Mars. Schiaparelli’s trip to the surface gained a large amount of data, but suffered a crash landing. However, TGO’s Mars Orbit Insertion was successfully completed.
The Exobiology on Mars project – ExoMars – is an ambitious, three-way cooperative venture between the European Space Agency (ESA), the Italian Space Agency (ASI), and the Russian Federal Space Agency (Roscosmos).
Like most missions, ExoMars has been through an intense series of birthing pangs originating in large part due to its international cooperative venture.
In July 2009, NASA announced the Mars Exploration Joint Initiative (MEJI) with ESA – the mission concept that would eventually become ExoMars.
Under the MEJI proposal, the mission would have utilized an Atlas V rocket to launch a rover and the Mars Trace Gas Orbiter (TGO) to the red planet.
MEJI was viewed as a joint partnership to allow ESA’s Aurora project – approved in 2005 – to receive joint funding from NASA to launch a rover with a stationary ground platform to Mars.
Aurora had, until 2009, been penciled in to launch aboard a Russian Soyuz Fregat rocket in 2011.
The new MEJI agreement, however, severely reduced the mission’s rover component to meet weight requirements of the Atlas V.
As the mission evolved, it was subsequently divided into a multi-spacecraft venture over two Atlas V launches.
Under this new two-launch plan, the rover would shift to a later launch window in 2018, thus allowing the TGO and a stationary meteorological platform to launch together in January 2016 – the architecture that would ultimately become ExoMars.
In August 2009, ESA and Roscosmos subsequently announced a contract for cooperation on two Mars exploration projects – Fobos-Grunt in 2014 and the ExoMars rover in 2018.
The 2009 ESA-Russia agreement specifically secured a Russian Proton rocket as a backup launcher for the ExoMars rover in 2018 should Atlas V be unable to meet the launch window and requirements.
From 2009 to 2011, preparation for the joint NASA-ESA mission continued on course, hitting its first major snag in April 2011 when NASA announced that the budget crisis facing the U.S. federal government would force a change to the ExoMars rover 2018 initiative.
This was then followed on 13 February 2012 by a termination of NASA’s participation in the entirety of the ExoMars project due to budgetary restraints in order to pay for cost overruns of the agency’s long-awaited James Webb Space Telescope.
One year later, ESA and Roscosmos officially signed a full partnership agreement for both ExoMars missions.
Under the new agreement, Roscosmos supplied both missions with Proton launch vehicles with Briz-M upper stages and launch services as well as additional Entry, Descent, and Landing module technology for the rover mission – which was, at that point, still scheduled for 2018.
The ESA and Roscosmos agreement saw Roscosmos include two Russian instruments initially developed for the Fobos-Grunt mission, which failed to leave Earth orbit in 2011, and a complete sharing of the intellectual property from the scientific results of the mission between ESA and the Russian Academy of Sciences.
Nevertheless, the withdrawal of NASA from both facets of the mission created severe budgetary issues for the mission.
Those issues persist to this day and have resulted in a two-year delay to the ExoMars rover mission from 2018 to 2020.
Regardless, a specific set of mission objectives were developed for the ExoMars mission, including, in order of priority, to: search for possible biosignatures of Martian life, past or present; characterize the water and geochemical distribution as a function of depth in the shallow subsurface; study the surface environment and identify hazards to future manned missions to Mars; investigate the planet’s subsurface and deep interior to better understand the evolution and habitability of Mars; achieve incremental steps ultimately culminating in a sample return flight.
Moreover, the mission carries a set of four technological objectives, including: landing of large payloads on Mars; to exploit solar electric power on the surface of Mars; to access the subsurface with a drill able to collect samples down to a depth of 2 metres (6.6 ft); to develop surface exploration capability using a rover.
In total, the scientific and technological objectives are spread over both the ExoMars 2016 and 2020 missions – with the final three technological objectives relating to solar electric power, subsurface drilling, and surface exploration with a rover falling to the 2020 rover mission
With the Russian and ESA partnership formalized, ESA and Roscosmos set about building the instruments and the spacecraft itself for the Trace Gas Orbiter while ASI took responsibility for the construction of the Schiaparelli lander.
After both the TGO and Schiaparelli were constructed and tested, they were shipped to the Baikonur Cosmodrome in Kazakhstan, where they were integrated to the Proton-M rocket in mid-January 2016.
Final checkouts of the spacecraft and the integrated Proton-M rocket were then carried out – with extreme care taken to ensure that all of the Proton-M’s systems were at 100% operating condition.
With final checkouts complete, the Proton-M rocket was rolled to launch pad 39 at Site 200 at Baikonur.
Lift off of the first ExoMars mission occurred at 09:31 GMT on 14 March 2016 with the Proton rocket performing flawlessly through the four burns over the course of 10 hours needed to initially insert TGO and Schiaparelli into Earth orbit before then propelling them through the TMI burn.
At 21:29 GMT that same day, the TGO successfully transmitted a signal back to its command base that the two spacecraft were functioning properly.
However, shortly after TGO and Schiaparelli separated from the Briz-M upper stage, ground tracking stations noted the presence of a large cluster of small debris where the Briz-M upper stage should have been.
While Russia denied any issue with the upper stage, it was widely understood that the Briz-M exploded shortly after releasing TGO and Schiaparelli on their independent course for Mars.
Successfully on their way, TGO and Schiaparelli entered a seven month cruise phase through the void between Earth and Mars for an anticipated October arrival at the red planet.
Designed as an Entry, Descent, and Landing Demonstrator Module (EDM), the Schiaparelli lander is a pathfinder element of the ExoMars 2016 project.
Schiaparelli was built by ASI to provide ESA and Roscosmos the opportunity to test landing technology on the surface of Mars ahead of the planned 2020 rover mission.
Of particular note for Schiaparelli, the lander is not equipped with solar arrays or a Radioactive Thermoelectric Generator (RTG) to provide sustained power.
Instead, Schiaparelli is equipped with a non-rechargeable electric battery that will allow it to remain active on the surface of Mars for anywhere between two to eight sols – with one sol being a single Martian day.
When NASA pulled out of ExoMars and Russia stepped in, Roscosmos initially offered the contribution of a 100-watt RTG power source; however, Russian export control procedures would not allow such technology to pass to a foreign power, so a non-rechargeable battery was chosen instead.
The lander itself is named after the 19th century astronomer Giovanni Schiaparelli, who is best known for his detailed descriptions of Martian surface features and also for being the first astronomer to determine the relationship between cometary debris and yearly meteor showers.
To obtain its primary mission objective of providing a technology demonstration for a controlled landing with pinpoint orientation and touchdown velocity, Schiaparelli was built with a diameter of 2.4 meters (7.9 ft) and a height of 1.65 m (5.4 ft).
The entire craft carries a mass of 600 kg (1,300 lbs).
To prepare for the all critical atmospheric entry, the TGO and Schiaparelli combined crafts were initially aimed at the Meridiani Planum on Mars in order to minimize the amount of propellant Schiaparelli would have to use to fine-tune its trajectory post-TGO separation/pre-Martian atmospheric entry.
Separation of Schiaparelli from the TGO occurred as scheduled on 16 October 2016 at 14:42 GMT, three days before the craft’s arrival at the red planet.
Once separation was confirmed, Schiaparelli successfully entered hibernation mode to save battery power as it continued its cruise toward the Martian atmosphere.
Targeting the Meridiani Planum (the same location currently being explored by NASA’s Opportunity rover), the Schiaparelli lander slammed into the Martian atmosphere at 14:42 GMT (10:42 EDT) at a velocity of 21,000 km/h (13,000 mph), bleeding off much of this entry force via a Norcoat Liege heat shield which was oriented in the direction of travel.
Once through the main part of atmospheric heating, the entry shell deployed two hypersonic parachutes at an altitude of 11 km (6.8 miles).
The parachutes further slowed the craft as its closed-loop guidance, navigation, and control system used a Doppler radar altimeter sensor and onboard inertial measurement units to begin aligning the craft toward its targeted landing location.
Once the onboard landing systems detect that Schiaparelli had reached 7 km (4.3 miles) in altitude, the heat shield separated from the base of the craft.
The rear heat shield then separated at 1.3 km (0.8 miles) altitude, and Schiaparelli emerged from its clamshell enclosure to begin the final stage of landing – a three clusters of three hydrazine pulse-firing liquid fuel engine retrorocket descent that was designed to slow the craft and bring it to an altitude of approximately 2 meters (6.5 ft) above the ground.
Once at this altitude, the retrorockets were supposed to have ceased, and the craft was to have performed a low-altitude crash landing onto the surface of Mars – with its final touchdown impact of 4 kph (3.1 mph) cushioned by a crushable structure at the base of the lander.
In total, from first atmospheric contact at 14:42 GMT, the entire descent and landing sequence was expected to take about six minutes.
Landing was expected at 14:48 GMT, with confirmation arriving back on Earth via an experimental, direct link with the 30-Telescope Giant Metrewave Radio Telescope in India at 14:56:45 GMT.
Data was lost via this communication path after the events through to the the chute deployment was recorded. Further attempts to relay data have been unsuccessful as ESA worked through the night on information passed on via assets.
Remarkably, this experimental link worked perfectly – with GMRT carrying a solid link through Mars approach and entry.
The only time it didn’t have a link was during plasma stage entry blackout – which was expected.
Currently, it is understood from ESA control that the signal lock confirmed all EDL operations through Schiaparelli’s release from its parachutes.
According to ESA control, the experimental signal tracked Schiaparelli to “near the landing location” before the signal stopped abruptly.
The Mars Express spacecraft then transmitted its stored landing data Schiaparelli sent to it back to Earth over the course of 90mins.
NASA’s Mars Reconnaissance Orbiter also passed over Schiaparelli’s targeted landing site and attempted to make contact with the craft, while the TGO also sent back data. As, such, engineers have data from the Pune radio telescope, Mars Express, potentially MRO and also TGO herself.
ESA provided an update at 10am local time (Germany) on Thursday.
Mission managers noted the data has now been partially analyzed and confirmed that the entry and descent stages occurred as expected, with events diverging from what was expected after the ejection of the back heat shield and parachute.
“This ejection itself appears to have occurred earlier than expected, but analysis is not yet complete,” they concluded.
“The thrusters were confirmed to have been briefly activated although it seems likely that they switched off sooner than expected, at an altitude that is still to be determined.”
As such, while they are yet to admit to it, the lander likely hit the surface at a much higher velocity than required.
“Following yesterday’s events we have an impressive orbiter around Mars ready for science and for relay support for the ExoMars rover mission in 2020,” said Jan Wörner, ESA’s Director General.
“Schiaparelli’s primary role was to test European landing technologies. Recording the data during the descent was part of that, and it is important we can learn what happened, in order to prepare for the future.”
“In terms of the Schiaparelli test module, we have data coming back that allow us to fully understand the steps that did occur, and why the soft landing did not occur,” said David Parker, ESA’s Director of Human Spaceflight and Robotic Exploration.
“From the engineering standpoint, it’s what we want from a test, and we have extremely valuable data to work with. We will have an enquiry board to dig deeper into the data and we cannot speculate further at this time.”
Images gained from NASA’s MRO later showed an impact zone for both the parachute and the lander. The latter showing the craft hit the surface at about 186 mph. It’s highly likely the craft’s prop tanks exploded as it impacted.
Had the lander survived, which is now unlikely, Schiaparelli was scheduled to spend 2-8 sols monitoring the local weather environment – including wind speed and direction, humidity, pressure, surface temperature, and transparency in the atmosphere.
While it might seem odd that Schiaparelli was targeted for a location currently being explored by another robotic mission, the Meridiani Planum was specifically chosen due to the fact that it is currently dust storm season at this region.
Thus, Meridiani Planum provided a prime opportunity to monitor and provide direct measurements of the dust-loaded atmosphere during entry and descent operations as well as surface measurements of a dust-rich environment.
After all, it’s possible that future human missions might have to land in dust-storm prone areas of Mars.
To this end, Schiaparelli carried the meteorological DREAMS (Dust characterization, Risk assessment, and Environment Analyser on the Martian Surface) experiment package that would allow for, among other things, the first-ever measurements of electric fields on the surface of Mars and their interaction with dust lifting mechanisms in the creation of Mars’ famous dust storms.
Moreover, as Schiaparelli executed its landing sequence and descends to the surface of Mars, ESA teams used the 30-Telescope Giant Metrewave Radio Telescope (GMRT) as an experimental receiver to detect the extremely faint signals from Schiaparelli directly. That was a partial succuess through to the loss of data near the fateful end of the journey to the surface.
The hope here is that future lander missions might be able to avoid the need for orbital repeaters of their signals back to Earth from craft pre-positioned in orbit of Mars – a potential new redundancy to current communication structures of arriving spacecraft at Mars.
Trace Gas Orbiter:
To prepare for the all critical atmospheric entry of Schiaparelli, the TGO and Schiaparelli combined crafts were initially aimed at the Meridiani Planum on Mars.
Separation of Schiaparelli from the TGO occurred as scheduled on 16 October 2016 at 14:42 GMT; however, while Schiaparelli separated successfully, there were initial concerns within mission control that an off-nominal had event occurred.
While separation was initially confirmed via a Doppler Shift of the Low Gain Antenna carrier signal from the TGO, leading to an initial confirmation of separation at 15:04 GMT, the determination of Schiaparelli separation was subsequently reclassified as “unambiguous” via Doppler Shift measurements at 15:27 GMT.
At the same time, reacquisition of the telemetry signal from the TGO did not happen.
By 15:30 GMT, ESA command confirmed that Schiaparelli had indeed separated from the TGO and reacquisition of a signal lock with the TGO had occurred – though the TGO was not transmitting telemetry as expected.
Finally, at 16:40 GMT, the TGO began returning telemetry along its High Gain Antenna comm line with ESA controllers.
While a lack of telemetry from the TGO was concerning in the moment, it could have led to greater ramifications mere hours later when the TGO was scheduled to perform a collision avoidance burn to correctly raise its approach path so that it would not slam into the surface of Mars like the Schiaparelli lander was designed to.
With full communication and telemetry established, the TGO successfully performed its 11.6-m/sec collision avoidance burn in the overnight hours of 17 October to successfully place itself into the correct trajectory for its Mars Orbit Insertion (MOI) burn.
With the collision avoidance burn complete, ESA controllers commanded the TGO into “hot redundancy mode” – a setting that prohibits the craft from defaulting into safe mode during the critical MOI burn.
According to ESA, “any routine problem that might arise – and that might trigger the craft to reset itself into ‘safe mode’ (which would shut down many ongoing activities, including propulsion) – will be ignored, so that the engine burn will in fact continue, more or less no matter what.”
On 18 October at 05:35 GMT, the MOI command sequence was confirmed to have been successfully uploaded into the TGO’s onboard computers.
The MOI burn was confirmed by information beamed back to Earth. The schedule called for the burn to begin at 13:04:47 GMT (09:04:47 EDT).
The MOI burn was designed to slow the TGO by just enough to be captured by Mars’ gravity field.
The MOI burn was scheduled to last 139-minutes, ending at 15:23 GMT and placed the TGO into Mars orbit.
Previously, ESA had given MOI burn times of 134 mins (which would put the end of the burn at 15:19:47 GMT) and 147 minutes (end of burn at 15:31 GMT) – though 139 minutes was used today.
Regardless, the burn was designed to place the TGO in a highly elliptical orbit of 300 x 96,000 km (186.4 x 59,651.6 miles).
In this orbit, the TGO will take 4 sols to complete a single orbit.
It will remain in this orbital configuration for two complete orbits – providing 8 sols worth of telecommunication relay operations for Schiaparelli with ESA controllers in Germany.
After Schiaparelli runs out of battery power, the TGO will begin a seven month-long series of aerobraking maneuvers with the Martian atmosphere to slowly stabilize and lower its altitude to its proper science orbit.
At present, the TGO is expected to begin its primary science mission in late 2017.
Once in its science orbit, the TGO will map hydrogen deposits at depths of up to 1 meter to search for evidence of water-ice deposits beneath the Martian surface.
This mapping endeavour could help identify places where future human missions to Mars could land to maximize in-situ resource utilization.
Overall, the TGO will help with an understanding of the spatial, temporal variation, and localization of atmospheric trace gases such as ethane, methane, and propane – all of which are potential indicators of biological processes.
Moreover, the TGO will also search for trace evidence of sulfur dioxide – which, if present with methane, would indicate not biological processes but rather geological processes.
To accomplish its science objectives, the TGO is outfitted with four scientific instruments: Nadir and Occultation for Mars Discovery (NOMAD); Atmospheric Chemistry Suite (ACS); Color and Stereo Surface Imaging System (CaSSIS); Fine Resolution Epithermal Neutron Detector (FREND).
NOMAD, a Belgian designed instrument, is designed to take spectroscopic observations of Mars in two infrared and one ultraviolet bands.
ACS, one of Russia’s two instruments, will examine Mars in three different infrared spectrometer bands.
Together with NOMAD, ACS will provide the most extensive spectral mapping of Mars to date – with an ability to detect trace particles in the parts-per-billion (ppb) level.
CaSSIS, a Switzerland developed instrument, will provide high-resolution (4.5 m/pixel) color stereo images of Mars that will help create highly accurate elevation level maps of Mars’ surface – aiding future Mars missions by helping better define potential landing sites on the red planet.
Meanwhile, FREND – the second of Roscosmos’ instruments – will help detect hydrogen in the top meter of Mars’ surface in the ever-ongoing search for water on Mars.
In addition to its science mission, the TGO will also serve – as many other Mars orbiters do – as a telecommunications relay through at least 2022.
(Images: Roscosmos, ESA, Italian Space Agency)