ExoMars, the next departure for the Red Planet, is set to lift off from Baikonur on 14 March 2016, and the teams here at ESOC are in absolute high gear getting ready to go. The ExoMars flight director, Michel Denis, and the spacecraft operations manager, Peter Schmitz, who, despite being completely absorbed in launch and LEOP preparations, have kindly taken time to explain the mission operations concepts and activities behind ExoMars/TGO. Today's Big Blog Post aims to provide as much of this information as possible, highlighting the most important aspects of the mission operations activities, centred primarily on the mission control team at ESOC (a somewhat different version appears in this web article). We've also cited the crucial involvement of the science operations team at ESAC and the industry support teams at TAS (I&F), who will oversee the entry, descent and landing of Schiaparelli. As always: the dates, times and sequence of events described below are subject to change.
Artist’s impression depicting the separation of the ExoMars 2016 entry, descent and landing demonstrator module, named Schiaparelli, from the Trace Gas Orbiter, and heading for Mars. TGO will be launched in 2016 with Schiaparelli, the entry, descent and landing demonstrator module. It will search for evidence of methane and other atmospheric gases that could be signatures of active biological or geological processes on Mars. TGO will also serve as a communications relay for the rover and surface science platform that will be launched in 2018. Credit: ESA–D. Ducros
There are two missions in the ExoMars programme: one comprises the Trace Gas Orbiter (TGO) plus an Entry, Descent and Landing Demonstrator Module (EDM), dubbed Schiaparelli, launch in 2016, and the other, comprising a rover, with a launch date of 2018. Both missions are in cooperation with Roscosmos.
The 2016 ExoMars TGO carries scientific instruments to detect and study atmospheric trace gases, such as methane. EDM contains sensors to evaluate the lander’s performance as it descends, and additional sensors to study the environment at the landing site.
In addition to its prime science mission, the orbiter also carries a sophisticated radio relay capability provided by NASA. The Electra Proximity Payload (Electra) is a telecommunications package that acts as a communications relay and navigation aid.
During its operational lifetime, the ExoMars TGO will perform three key roles:
- Conduct investigations into the biological or geological origin of trace gases on Mars with a scientific payload of four instruments;
- Deliver Schiaparelli and support part of the data transmission during its descent and surface operations;
- Serve as a data relay platform to support communications for the ExoMars 2018 rover and the surface science platform, as well as partner agency rovers.
TGO and Schiaparelli will go through several mission phases and pass a number of critical milestones in order to arrive at Mars and begin routine science observations, including:
- Launch, set for 14 March 2016
- Commissioning and cruise phase: almost 500 million km to go
- Mid-course deep-space manoeuvre (to adjust trajectory for Mars arrival)
- Separation: dispatch Schiaparelli to the surface
- Entry, descent and landing of Schiaparelli
- TGO manoeuvres, to be captured by Mars gravity into its initial orbit
- Aerobraking, to lower TGO to its final 400 x 400 km science orbit (Nov 2017)
Launch
- 14 March 2016 09:31:42 UTC – Lift off from Baikonur on a powerful Russian Proton-M launcher
- 14 March 2016 20:12:45 UTC – ExoMars/TGO separation from Proton's Breeze-M upper stage; departure on interplanetary transfer orbit
- 14 March 2016 21:28:26 UTC – Receipt of first signals from ExoMars/TGO after launch (AOS ) over Malindi station in Africa; signals relayed to ESOC, ESA's mission control centre, Darmstadt, Germany
After separation, command and control of ExoMars/TGO will be taken over by ESA’s mission control teams at ESOC, who will operate both TGO and the Schiaparelli Entry, Descent and Landing Demonstrator Module (EDM) throughout their missions . At ESOC, the ExoMars Flight Control Team are supported by experts from flight dynamics, ground stations and software systems to conduct full-time mission control. Once Schiaparelli separates and later lands, its mission will be automated, based on settings primarily developed by ESA’s industrial partners.
On launch day – Contact between mission controllers and ExoMars/TGO is maintained via the Italian space agency (ASI)’s 2m dish antenna at Malindi, Kenya, and by ESA’s 15m ground stations at Maspalomas, Spain, and Kourou, French Guiana. Flight dynamics experts at ESOC will perform the first ‘orbit determination’ for ExoMars/TGO after gathering radiometric data via Maspalomas station.
En route to Mars
Subsequently, as the craft embarks on its journey to Mars, tracking and telecommanding duties are handed over to ESA's 'Big Iron' – the 35m-diameter deep-space tracking stations at Malargüe, Argentina, and New Norcia, Australia. These two stations in can provide 24 hr/day communication coverage. Both are part of ESA’s tracking station network – Estrack – a global system of ground stations operated from ESOC. As Mars presently orbits below the ecliptic plane, ground stations in the southern hemisphere are especially suited for establishing daily radio contact.
Until 24 April – En route to Mars, the ExoMars/TGO spacecraft is now in the commissioning phase and mission control teams at ESOC and science operations teams at ESAC, ESA’s establishment near Madrid, Spain , check out, verify and test all systems and instruments. The Schiaparelli lander will similarly be checked out by industrial teams from Thales Alenia Space (Italy).
Daily communication passes are provided by New Norcia station during daylight hours in Darmstadt, with additional support from Malargüe station as required.
In early April, the NASA radio transponder will be switched on and tested by a joint ESA-NASA team to ensure its correct functioning, non-interference with the TGO imaging payload and the ability to work with ESA and NASA ground stations . This device will play a crucial role once TGO is in routine orbit at Mars, providing daily data relay services for NASA and ESA rovers on the Martian surface.
Until end-June – ExoMars/TGO enters the cruise phase as it continues enroute to Mars; on-board activities are relatively quiet and ground station passes are only scheduled three times weekly. Mission control teams continue verifying and confirming the health and functionality of TGO and Schiaparelli in the harsh environment of interplanetary space.
Mid July – Until mid-August: Teams at ESOC will conduct a series of ultra-precise navigation measurements known as 'delta-DOR', for 'Delta-differential One-Way Ranging'. This advanced technique uses signals received from quasars deep in our Milky Way galaxy to correct the radio signals received from ExoMars/TGO, resulting in an extremely precise position determination. How precise? The spacecraft’s position in space can be fixed on the order of just several hundred metres at a distance of 100 000 000 km. Results will be used to calculate the upcoming mid-course correction manoeuvre (also called the ‘deep-space manoeuvre’). A second Delta-DOR campaign in September-October will generate results that will help determine the Mars orbit injection for TGO and the final Schiaparelli descent trajectory.
Mid-course correction burn
28 July – TGO carries out one of the most critical activities during the voyage to Mars: a very large engine burn in deep space that changes its direction and velocity by some 326 m/second . This mid-course trajectory correction manoeuvre will line the spacecraft up to intersect the Red Planet on 19 October.
Until 19 October – The work of the mission control teams is becoming steadily more intense, and ESA's Estrack ground stations are now providing daily telecommanding passes. In the final ten days before arrival, New Norcia and Malargüe ground stations will provide 24 hrs/day radio contact as engineers at ESOC carefully monitor the spacecraft and plan its complex orbit-entry activities. The final commands for the Schiaparelli EDM will be prepared and uploaded, and all systems on both TGO and Schiaparelli will be thoroughly checked out in the run up to arrival.
Arrival
16 October 2016 14:42 UTC – Start of critical arrival activities. TGO will eject Schiaparelli, dispatching it on a three-day descent to the surface. Prior to separation, TGO will perform a ‘slew’, rotating about its axes to a specific orientation in space such that only its low-gain antenna will face Earth. As a result, ESA will enlist the support of NASA's giant 70m Deep Space Network (DSN) ground stations at Canberra, Australia , and Madrid, Spain, to listen for the spacecraft's signals as the EDM module separates. Schiaparelli will be pushed away from TGO 30 cm/second, but this tiny push can be detected by the DSN stations.
Schiaparelli will be dispatched on a direct intercept course toward Mars, spinning at 2.75 rpm for stability, on track to enter the atmosphere and conduct a challenging descent and landing on 19 October, lowering itself to the surface for a soft landing under parachutes. Its systems will remain in hibernation until waking up 75 minutes before atmosphere entry.
17 October 2016 – About 12 hours after Schiaparelli has separated, the ExoMars/TGO orbiter will conduct an ‘orbit raising manoeuvre’ – a modest but crucial engine burn (it runs just a few minutes) that must provide a change in direction, raising its trajectory to several hundred kilometres above the planet (otherwise, like Schiaparelli, TGO, too, would intersect the surface on 19 October). This manoeuvre will line the craft up for a second critical burn on 19 October, which will slow it sufficiently to be captured by Mars’ gravity.
If for any reason Schiaparelli fails to separate from TGO on 16 October, there is a back-up separation slot available on 17 October1.
During the critical arrival activities, several of NASA’s 34m deep-space stations will provide a ‘hot back-up’ to ESA’s Estrack stations, ensuring that there is no loss of communication at a time when any delay in commanding could have serious effect on orbit entry or landing.
19 October – Arrival Day for TGO/Landing Day for Schiaparelli. Three days after separation, TGO and Schiaparelli each undergo the most critical portions of their journey to Mars.
Schiaparelli – Entry, Descent and Landing (EDL)
Continuing on its post-separation ballistic orbit, the 600-kg Schiaparelli will wake up 75 minutes prior to entering the Martian atmosphere, expected at 14:42 UTC , at an altitude of 122.5 km and a speed of approximately 21 000 km/hour. An aerodynamic heatshield will protect Schiaparelli from the severe heat flux and deceleration, so that at an altitude of about 11 km, when the 12 m- diameter parachute is deployed, it will be travelling at around 1650 km/hour.
Descending under its parachute, Schiaparelli will release its front heatshield at an altitude of about 7 km and turn on its Doppler radar altimeter, which can measure the distance to the ground and its velocity relative to the surface. This information is used to activate and command the propulsion system once the rear heatshield and parachute have been jettisoned 1.3 km above the surface.
Between 1300 m and 2 m altitude, the propulsion system will slow it from 270 km/hour to just 7 km/hour; at that height, the engines will be switched off and Schiaparelli will free-fall to the ground, where the final impact, at just under 11 km per hour, will be cushioned by a crushable structure on the base of the lander.
Schiaparelli will target a landing site on the plain known as Meridiani Planum. This area interests scientists because it contains an ancient layer of hematite, an iron oxide that, on Earth, almost always forms in an environment containing liquid water.
Mars Express listens in
During Schiaparelli’s critical EDL phase on 19 October, ESA’s Mars Express probe, which has been orbiting the Red Planet since 2003, will monitor and record signals from the module.
This so-called ‘open-loop’ recording will enable Mars Express to detect critical events such as parachute deployment, heatshield jettisoning, touch down and start of operations on the surface, which will be relayed immediately thereafter to mission controllers at ESOC2.
The amount of Schiaparelli signal data recorded by Mars Express will be kept small, so that the recorded information can be quickly relayed to Earth. On 19 October, signals will take 9min:46sec to travel from Mars to Earth. Receipt of this recording, about 60 minutes after actual descent, will provide the first in-situ confirmation on Earth of Schiaparelli’s arrival and landing (first confirmation at Earth will come from the GMRT recordings – see below).
Upon landing, Schiaparelli will commence surface science operations, lasting until approximately 23 October.
Ground recording campaign
Schiaparelli’s descent is also expected to be recorded on Earth by scientists using the Giant Metrewave Radio Telescope (GMRT), located near Pune in India. GMRT comprises an array of 30 radio telescopes (each with a dish diameter of 45 m ) operated by the National Centre for Radio Astrophysics, a part of the Tata Institute of Fundamental Research, Mumbai, and it is one of the world's largest interferometric arrays.
To enable recording of Schiaparelli’s signal across the 206 million kms between Earth and Mars on 19 October, the GMRT will be augmented with radio science equipment developed at NASA's Jet Propulsion Laboratory (JPL), which was designed to record the entry and descent of NASA’s InSight Mars lander as well as ExoMars/Schiaparelli. InSight’s original March 2016 launch is now delayed, and so the equipment will now first record Schiaparelli’s descent .
A joint JPL/GMRT team will record the descent signals, and make the recorded plot immediately available to mission controllers at ESOC, providing first confirmation of Schiaparelli’s arrival.
This activity promises to provide an extremely important confirmation of the Module’s descent and landing, and signifies a major area of international cooperation between ESA, NASA and India for the Schiaparelli mission.
ExoMars/TGO – Mars Orbit Entry
On the same day, 19 October, the TGO orbiter will carry out two critical activities, virtually at the same time.
First, it will use its radio system to record signals from Schiaparelli during its descent to the surface, similar to Mars Express. This information will be stored on board and later transmitted to Earth, where it will be processed at ESOC to extract telemetry and other information to enable a detailed reconstruction of the descent profile and the functioning of the module under the extreme conditions of atmospheric entry. Due to time necessary to download this large volume of data, and the time necessary to analyse it at ESOC, it will not be available until a number of hours after EDL.
Second, it will conduct a critical engine burn, using its 424-N main engine to conduct the Mars Orbit Insertion (MOI) manoeuvre. This manoeuvre will slow TGO by 1550 m/sec, sufficient to be captured into an initial Mars orbit (a double what was needed for Mars Express capture in 2003), and will last about 134 minutes, beginning at 13:09 UTC on 19 October.
This absolutely critical manoeuvre will be tracked by ESA and NASA 70m ground stations , which will provide a live feed of progress to mission controllers at ESOC. Successful completion of the burn, expected at 15:23 UTC , will mark the second time Europe has placed a spacecraft into orbit around the Red Planet.
The initial highly eccentric orbit is dubbed the ‘4 Sol’ orbit, as it will take TGO four Martian days to complete one revolution, with its altitude above Mars varying between 298 km and 95 856 km .
Successful capture by Mars means that TGO can begin a lengthy series of orbital adjustments.
In-orbit
11 January 2017 – TGO orbital inclination will be adjusted to 74°, which is optimised for its science and radio relay missions. On 17 January 2017 , it will perform an Apoares-reduction manoeuvre to go from the initial 4-Sol orbit to a 1-Sol orbit.
January – November 2017 – TGO will employ sophisticated aerobraking techniques – the first time ESA will do so to attain a science orbit around another body in our Solar System – to steadily lower itself to a circular, 400-km orbit.
With aerobraking, the TGO solar arrays will be used to generate tiny amounts of drag due to the wisps of Martian atmosphere at very high altitudes, which will slow the craft and lower its orbit. While aerobraking takes time, it uses very little fuel and will itself provide scientific insight into the dynamics of Mars’ atmosphere. With ExoMars 2016, it will be the first time ESA uses aerobraking for an extended period of time to attain a science orbit around another body in our Solar System.
The TGO science and radio relay missions will begin in December 2017.
TGO radio relay
TGO features a sophisticated radio relay capability provided by NASA. The Electra system, more formally called the ‘Electra Proximity Payload’, is a telecommunications package that acts as a communications relay and navigation aid. It comprises twin ultra-high frequency (UHF) radios and will provide communication links between Earth and craft on the Martian surface – rovers or landers.
The relay of information from Mars surface craft to Mars orbiters, then from Mars orbit to Earth, enables receiving much more data from the surface missions than would otherwise be possible.
TGO will provide daily data relay services to NASA’s Curiosity and MER-B (Opportunity) rovers currently on the surface, as well as to the InSight lander and ESA’s ExoMars 2018 rover. It will also support Russia’s 2018 lander and future NASA rovers.
ESA is now establishing a new European Relay Coordination Office (ERCO) at ESOC to manage scheduling, planning and day-to-day control of the service, which will also employ ESA, NASA and Russian ground stations for download, receipt and distribution of the scientific data.
ERCO will make use of sophisticated new techniques to conduct relay coordination on a semi-automated basis, making it the central European hub for relay of precious scientific data between landers and orbiters at Mars.
Flying NASA’s Electra payload with its advanced data relay capabilities on board ESA’s TGO orbiter marks a significant deepening of cross-agency cooperation and mutual support at Mars.
Notes:
Note1: If the Schiaparelli EDM module fails to function, or fails to separate as nominally planned, it can be discarded by the TGO orbiter, whose mass would then be reduced sufficiently to conduct orbit entry on 19 October. If for any reason Schiaparelli does not separate before 18 October, and remains attached to TGO, the orbiter’s engine would be unable to provide sufficient thrust to slow the combined mass of TGO-plus-Schiaparelli in time to be captured into Mars orbit on 19 October. In this case, the pair would perform a flyby and escape into a heliocentric orbit that would bring them back to Mars in two years’ time. Then, there would be sufficient time to conduct the longer burn necessary to slow the duo enough to be captured by Martian gravity. It’s all a function of orbital dynamics, mass, gravity and thrust.
Note2: If Schiaparelli lands nominally, then its signals will continue after the expected touch-down time. If signals end abruptly, this would be an indication that the lander is not functioning on the surface as expected.
from Rocket Science http://ift.tt/221mWxS
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ExoMars, the next departure for the Red Planet, is set to lift off from Baikonur on 14 March 2016, and the teams here at ESOC are in absolute high gear getting ready to go. The ExoMars flight director, Michel Denis, and the spacecraft operations manager, Peter Schmitz, who, despite being completely absorbed in launch and LEOP preparations, have kindly taken time to explain the mission operations concepts and activities behind ExoMars/TGO. Today's Big Blog Post aims to provide as much of this information as possible, highlighting the most important aspects of the mission operations activities, centred primarily on the mission control team at ESOC (a somewhat different version appears in this web article). We've also cited the crucial involvement of the science operations team at ESAC and the industry support teams at TAS (I&F), who will oversee the entry, descent and landing of Schiaparelli. As always: the dates, times and sequence of events described below are subject to change.
Artist’s impression depicting the separation of the ExoMars 2016 entry, descent and landing demonstrator module, named Schiaparelli, from the Trace Gas Orbiter, and heading for Mars. TGO will be launched in 2016 with Schiaparelli, the entry, descent and landing demonstrator module. It will search for evidence of methane and other atmospheric gases that could be signatures of active biological or geological processes on Mars. TGO will also serve as a communications relay for the rover and surface science platform that will be launched in 2018. Credit: ESA–D. Ducros
There are two missions in the ExoMars programme: one comprises the Trace Gas Orbiter (TGO) plus an Entry, Descent and Landing Demonstrator Module (EDM), dubbed Schiaparelli, launch in 2016, and the other, comprising a rover, with a launch date of 2018. Both missions are in cooperation with Roscosmos.
The 2016 ExoMars TGO carries scientific instruments to detect and study atmospheric trace gases, such as methane. EDM contains sensors to evaluate the lander’s performance as it descends, and additional sensors to study the environment at the landing site.
In addition to its prime science mission, the orbiter also carries a sophisticated radio relay capability provided by NASA. The Electra Proximity Payload (Electra) is a telecommunications package that acts as a communications relay and navigation aid.
During its operational lifetime, the ExoMars TGO will perform three key roles:
- Conduct investigations into the biological or geological origin of trace gases on Mars with a scientific payload of four instruments;
- Deliver Schiaparelli and support part of the data transmission during its descent and surface operations;
- Serve as a data relay platform to support communications for the ExoMars 2018 rover and the surface science platform, as well as partner agency rovers.
TGO and Schiaparelli will go through several mission phases and pass a number of critical milestones in order to arrive at Mars and begin routine science observations, including:
- Launch, set for 14 March 2016
- Commissioning and cruise phase: almost 500 million km to go
- Mid-course deep-space manoeuvre (to adjust trajectory for Mars arrival)
- Separation: dispatch Schiaparelli to the surface
- Entry, descent and landing of Schiaparelli
- TGO manoeuvres, to be captured by Mars gravity into its initial orbit
- Aerobraking, to lower TGO to its final 400 x 400 km science orbit (Nov 2017)
Launch
- 14 March 2016 09:31:42 UTC – Lift off from Baikonur on a powerful Russian Proton-M launcher
- 14 March 2016 20:12:45 UTC – ExoMars/TGO separation from Proton's Breeze-M upper stage; departure on interplanetary transfer orbit
- 14 March 2016 21:28:26 UTC – Receipt of first signals from ExoMars/TGO after launch (AOS ) over Malindi station in Africa; signals relayed to ESOC, ESA's mission control centre, Darmstadt, Germany
After separation, command and control of ExoMars/TGO will be taken over by ESA’s mission control teams at ESOC, who will operate both TGO and the Schiaparelli Entry, Descent and Landing Demonstrator Module (EDM) throughout their missions . At ESOC, the ExoMars Flight Control Team are supported by experts from flight dynamics, ground stations and software systems to conduct full-time mission control. Once Schiaparelli separates and later lands, its mission will be automated, based on settings primarily developed by ESA’s industrial partners.
On launch day – Contact between mission controllers and ExoMars/TGO is maintained via the Italian space agency (ASI)’s 2m dish antenna at Malindi, Kenya, and by ESA’s 15m ground stations at Maspalomas, Spain, and Kourou, French Guiana. Flight dynamics experts at ESOC will perform the first ‘orbit determination’ for ExoMars/TGO after gathering radiometric data via Maspalomas station.
En route to Mars
Subsequently, as the craft embarks on its journey to Mars, tracking and telecommanding duties are handed over to ESA's 'Big Iron' – the 35m-diameter deep-space tracking stations at Malargüe, Argentina, and New Norcia, Australia. These two stations in can provide 24 hr/day communication coverage. Both are part of ESA’s tracking station network – Estrack – a global system of ground stations operated from ESOC. As Mars presently orbits below the ecliptic plane, ground stations in the southern hemisphere are especially suited for establishing daily radio contact.
Until 24 April – En route to Mars, the ExoMars/TGO spacecraft is now in the commissioning phase and mission control teams at ESOC and science operations teams at ESAC, ESA’s establishment near Madrid, Spain , check out, verify and test all systems and instruments. The Schiaparelli lander will similarly be checked out by industrial teams from Thales Alenia Space (Italy).
Daily communication passes are provided by New Norcia station during daylight hours in Darmstadt, with additional support from Malargüe station as required.
In early April, the NASA radio transponder will be switched on and tested by a joint ESA-NASA team to ensure its correct functioning, non-interference with the TGO imaging payload and the ability to work with ESA and NASA ground stations . This device will play a crucial role once TGO is in routine orbit at Mars, providing daily data relay services for NASA and ESA rovers on the Martian surface.
Until end-June – ExoMars/TGO enters the cruise phase as it continues enroute to Mars; on-board activities are relatively quiet and ground station passes are only scheduled three times weekly. Mission control teams continue verifying and confirming the health and functionality of TGO and Schiaparelli in the harsh environment of interplanetary space.
Mid July – Until mid-August: Teams at ESOC will conduct a series of ultra-precise navigation measurements known as 'delta-DOR', for 'Delta-differential One-Way Ranging'. This advanced technique uses signals received from quasars deep in our Milky Way galaxy to correct the radio signals received from ExoMars/TGO, resulting in an extremely precise position determination. How precise? The spacecraft’s position in space can be fixed on the order of just several hundred metres at a distance of 100 000 000 km. Results will be used to calculate the upcoming mid-course correction manoeuvre (also called the ‘deep-space manoeuvre’). A second Delta-DOR campaign in September-October will generate results that will help determine the Mars orbit injection for TGO and the final Schiaparelli descent trajectory.
Mid-course correction burn
28 July – TGO carries out one of the most critical activities during the voyage to Mars: a very large engine burn in deep space that changes its direction and velocity by some 326 m/second . This mid-course trajectory correction manoeuvre will line the spacecraft up to intersect the Red Planet on 19 October.
Until 19 October – The work of the mission control teams is becoming steadily more intense, and ESA's Estrack ground stations are now providing daily telecommanding passes. In the final ten days before arrival, New Norcia and Malargüe ground stations will provide 24 hrs/day radio contact as engineers at ESOC carefully monitor the spacecraft and plan its complex orbit-entry activities. The final commands for the Schiaparelli EDM will be prepared and uploaded, and all systems on both TGO and Schiaparelli will be thoroughly checked out in the run up to arrival.
Arrival
16 October 2016 14:42 UTC – Start of critical arrival activities. TGO will eject Schiaparelli, dispatching it on a three-day descent to the surface. Prior to separation, TGO will perform a ‘slew’, rotating about its axes to a specific orientation in space such that only its low-gain antenna will face Earth. As a result, ESA will enlist the support of NASA's giant 70m Deep Space Network (DSN) ground stations at Canberra, Australia , and Madrid, Spain, to listen for the spacecraft's signals as the EDM module separates. Schiaparelli will be pushed away from TGO 30 cm/second, but this tiny push can be detected by the DSN stations.
Schiaparelli will be dispatched on a direct intercept course toward Mars, spinning at 2.75 rpm for stability, on track to enter the atmosphere and conduct a challenging descent and landing on 19 October, lowering itself to the surface for a soft landing under parachutes. Its systems will remain in hibernation until waking up 75 minutes before atmosphere entry.
17 October 2016 – About 12 hours after Schiaparelli has separated, the ExoMars/TGO orbiter will conduct an ‘orbit raising manoeuvre’ – a modest but crucial engine burn (it runs just a few minutes) that must provide a change in direction, raising its trajectory to several hundred kilometres above the planet (otherwise, like Schiaparelli, TGO, too, would intersect the surface on 19 October). This manoeuvre will line the craft up for a second critical burn on 19 October, which will slow it sufficiently to be captured by Mars’ gravity.
If for any reason Schiaparelli fails to separate from TGO on 16 October, there is a back-up separation slot available on 17 October1.
During the critical arrival activities, several of NASA’s 34m deep-space stations will provide a ‘hot back-up’ to ESA’s Estrack stations, ensuring that there is no loss of communication at a time when any delay in commanding could have serious effect on orbit entry or landing.
19 October – Arrival Day for TGO/Landing Day for Schiaparelli. Three days after separation, TGO and Schiaparelli each undergo the most critical portions of their journey to Mars.
Schiaparelli – Entry, Descent and Landing (EDL)
Continuing on its post-separation ballistic orbit, the 600-kg Schiaparelli will wake up 75 minutes prior to entering the Martian atmosphere, expected at 14:42 UTC , at an altitude of 122.5 km and a speed of approximately 21 000 km/hour. An aerodynamic heatshield will protect Schiaparelli from the severe heat flux and deceleration, so that at an altitude of about 11 km, when the 12 m- diameter parachute is deployed, it will be travelling at around 1650 km/hour.
Descending under its parachute, Schiaparelli will release its front heatshield at an altitude of about 7 km and turn on its Doppler radar altimeter, which can measure the distance to the ground and its velocity relative to the surface. This information is used to activate and command the propulsion system once the rear heatshield and parachute have been jettisoned 1.3 km above the surface.
Between 1300 m and 2 m altitude, the propulsion system will slow it from 270 km/hour to just 7 km/hour; at that height, the engines will be switched off and Schiaparelli will free-fall to the ground, where the final impact, at just under 11 km per hour, will be cushioned by a crushable structure on the base of the lander.
Schiaparelli will target a landing site on the plain known as Meridiani Planum. This area interests scientists because it contains an ancient layer of hematite, an iron oxide that, on Earth, almost always forms in an environment containing liquid water.
Mars Express listens in
During Schiaparelli’s critical EDL phase on 19 October, ESA’s Mars Express probe, which has been orbiting the Red Planet since 2003, will monitor and record signals from the module.
This so-called ‘open-loop’ recording will enable Mars Express to detect critical events such as parachute deployment, heatshield jettisoning, touch down and start of operations on the surface, which will be relayed immediately thereafter to mission controllers at ESOC2.
The amount of Schiaparelli signal data recorded by Mars Express will be kept small, so that the recorded information can be quickly relayed to Earth. On 19 October, signals will take 9min:46sec to travel from Mars to Earth. Receipt of this recording, about 60 minutes after actual descent, will provide the first in-situ confirmation on Earth of Schiaparelli’s arrival and landing (first confirmation at Earth will come from the GMRT recordings – see below).
Upon landing, Schiaparelli will commence surface science operations, lasting until approximately 23 October.
Ground recording campaign
Schiaparelli’s descent is also expected to be recorded on Earth by scientists using the Giant Metrewave Radio Telescope (GMRT), located near Pune in India. GMRT comprises an array of 30 radio telescopes (each with a dish diameter of 45 m ) operated by the National Centre for Radio Astrophysics, a part of the Tata Institute of Fundamental Research, Mumbai, and it is one of the world's largest interferometric arrays.
To enable recording of Schiaparelli’s signal across the 206 million kms between Earth and Mars on 19 October, the GMRT will be augmented with radio science equipment developed at NASA's Jet Propulsion Laboratory (JPL), which was designed to record the entry and descent of NASA’s InSight Mars lander as well as ExoMars/Schiaparelli. InSight’s original March 2016 launch is now delayed, and so the equipment will now first record Schiaparelli’s descent .
A joint JPL/GMRT team will record the descent signals, and make the recorded plot immediately available to mission controllers at ESOC, providing first confirmation of Schiaparelli’s arrival.
This activity promises to provide an extremely important confirmation of the Module’s descent and landing, and signifies a major area of international cooperation between ESA, NASA and India for the Schiaparelli mission.
ExoMars/TGO – Mars Orbit Entry
On the same day, 19 October, the TGO orbiter will carry out two critical activities, virtually at the same time.
First, it will use its radio system to record signals from Schiaparelli during its descent to the surface, similar to Mars Express. This information will be stored on board and later transmitted to Earth, where it will be processed at ESOC to extract telemetry and other information to enable a detailed reconstruction of the descent profile and the functioning of the module under the extreme conditions of atmospheric entry. Due to time necessary to download this large volume of data, and the time necessary to analyse it at ESOC, it will not be available until a number of hours after EDL.
Second, it will conduct a critical engine burn, using its 424-N main engine to conduct the Mars Orbit Insertion (MOI) manoeuvre. This manoeuvre will slow TGO by 1550 m/sec, sufficient to be captured into an initial Mars orbit (a double what was needed for Mars Express capture in 2003), and will last about 134 minutes, beginning at 13:09 UTC on 19 October.
This absolutely critical manoeuvre will be tracked by ESA and NASA 70m ground stations , which will provide a live feed of progress to mission controllers at ESOC. Successful completion of the burn, expected at 15:23 UTC , will mark the second time Europe has placed a spacecraft into orbit around the Red Planet.
The initial highly eccentric orbit is dubbed the ‘4 Sol’ orbit, as it will take TGO four Martian days to complete one revolution, with its altitude above Mars varying between 298 km and 95 856 km .
Successful capture by Mars means that TGO can begin a lengthy series of orbital adjustments.
In-orbit
11 January 2017 – TGO orbital inclination will be adjusted to 74°, which is optimised for its science and radio relay missions. On 17 January 2017 , it will perform an Apoares-reduction manoeuvre to go from the initial 4-Sol orbit to a 1-Sol orbit.
January – November 2017 – TGO will employ sophisticated aerobraking techniques – the first time ESA will do so to attain a science orbit around another body in our Solar System – to steadily lower itself to a circular, 400-km orbit.
With aerobraking, the TGO solar arrays will be used to generate tiny amounts of drag due to the wisps of Martian atmosphere at very high altitudes, which will slow the craft and lower its orbit. While aerobraking takes time, it uses very little fuel and will itself provide scientific insight into the dynamics of Mars’ atmosphere. With ExoMars 2016, it will be the first time ESA uses aerobraking for an extended period of time to attain a science orbit around another body in our Solar System.
The TGO science and radio relay missions will begin in December 2017.
TGO radio relay
TGO features a sophisticated radio relay capability provided by NASA. The Electra system, more formally called the ‘Electra Proximity Payload’, is a telecommunications package that acts as a communications relay and navigation aid. It comprises twin ultra-high frequency (UHF) radios and will provide communication links between Earth and craft on the Martian surface – rovers or landers.
The relay of information from Mars surface craft to Mars orbiters, then from Mars orbit to Earth, enables receiving much more data from the surface missions than would otherwise be possible.
TGO will provide daily data relay services to NASA’s Curiosity and MER-B (Opportunity) rovers currently on the surface, as well as to the InSight lander and ESA’s ExoMars 2018 rover. It will also support Russia’s 2018 lander and future NASA rovers.
ESA is now establishing a new European Relay Coordination Office (ERCO) at ESOC to manage scheduling, planning and day-to-day control of the service, which will also employ ESA, NASA and Russian ground stations for download, receipt and distribution of the scientific data.
ERCO will make use of sophisticated new techniques to conduct relay coordination on a semi-automated basis, making it the central European hub for relay of precious scientific data between landers and orbiters at Mars.
Flying NASA’s Electra payload with its advanced data relay capabilities on board ESA’s TGO orbiter marks a significant deepening of cross-agency cooperation and mutual support at Mars.
Notes:
Note1: If the Schiaparelli EDM module fails to function, or fails to separate as nominally planned, it can be discarded by the TGO orbiter, whose mass would then be reduced sufficiently to conduct orbit entry on 19 October. If for any reason Schiaparelli does not separate before 18 October, and remains attached to TGO, the orbiter’s engine would be unable to provide sufficient thrust to slow the combined mass of TGO-plus-Schiaparelli in time to be captured into Mars orbit on 19 October. In this case, the pair would perform a flyby and escape into a heliocentric orbit that would bring them back to Mars in two years’ time. Then, there would be sufficient time to conduct the longer burn necessary to slow the duo enough to be captured by Martian gravity. It’s all a function of orbital dynamics, mass, gravity and thrust.
Note2: If Schiaparelli lands nominally, then its signals will continue after the expected touch-down time. If signals end abruptly, this would be an indication that the lander is not functioning on the surface as expected.
from Rocket Science http://ift.tt/221mWxS
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