19. November 2018

DLR's HP3 Mole on board NASA's In­Sight mis­sion soon to land on Mars

Artist impression of InSight entering the Martian atmosphere
In­Sight en­ter­ing the Mar­tian at­mo­sphere (artist im­pres­sion)
Image 1/8, Credit: DLR (CC-BY 3.0)

InSight entering the Martian atmosphere (artist impression)

Af­ter the cruise stage is jet­ti­soned, the land­ing probe will en­ter the Mar­tian at­mo­sphere at 20:47 CET at a speed of 3600 kilo­me­tres per hour. An in­ter­ven­tion in the land­ing pro­cess is not pos­si­ble: Since it takes a sig­nal from Earth to reach Mars 8 min­utes and 6 sec­onds, the land­ing will have al­ready tak­en place by the time the last sig­nal from In­Sight be­fore en­ter­ing the at­mo­sphere reach­es Earth. The probe will reach the sur­face sev­en min­utes af­ter at­mo­spher­ic en­try. About half a minute af­ter en­ter­ing the at­mo­sphere, the fric­tion of the gas molecules of the high at­mo­sphere will cause the heat shield to be­gin to glow at the tip at a tem­per­a­ture of about 1500 de­grees Cel­sius and then cool again. Peak de­cel­er­a­tion will hap­pen about 2 min­utes af­ter at­mo­spher­ic en­try 15 sec­onds lat­er, at up to 7.5 g. Be­fore the parachute is de­ployed, fric­tion be­tween the at­mo­sphere and the heat shield will re­move near­ly 99.5 per­cent of the en­try ve­hi­cle’s ki­net­ic en­er­gy.
InSight probe during a test
In­Sight probe dur­ing a test
Image 2/8, Credit: NASA/JPL-Caltech/Lockheed Martin.

InSight probe during a test

In­Sight's so­lar pan­els are de­ployed and the probe is test­ed in its de­ploy­ment con­fig­u­ra­tion dur­ing a test in the clean room. In the mid­dle of the plat­form, the pro­tec­tive cov­er of the seis­mome­ter SEIS, to the right of which is the heat flux probe HP³ de­vel­oped at DLR.
Map of the landing site for the InSight mission in Elysium Planitia
The land­ing site for the In­Sight mis­sion in Ely­si­um Plani­tia
Image 3/8, Credit: NASA/JPL/USGS (MOLA)

The landing site for the InSight mission in Elysium Planitia

For the In­Sight mis­sion, a land­ing area was sought that had to meet sev­er­al sci­en­tif­ic cri­te­ria, but above all space sys­tems en­gi­neer­ing cri­te­ria. For a se­cure en­er­gy sup­ply from so­lar pow­er and to avoid ex­treme di­ur­nal and sea­son­al tem­per­a­ture vari­a­tions, it could not be too far north or south of the equa­tor, it had to be flat and, as far as pos­si­ble, not cov­ered by rocks. Af­ter a long se­lec­tion pro­cess, en­gi­neers and sci­en­tists se­lect­ed an area in a plain south­west of the large vol­canic com­plex sur­round­ing Ely­si­um Mons. The cho­sen site is in Ely­si­um Plani­tia, north of the Mar­tian equa­tor and the high­land bor­der – just a few hun­dred kilo­me­tres north of Gale Crater (be­low the ‘4’ in the lat­i­tude la­bel), in which the NASA rover Cu­rios­i­ty has been driv­ing since 2012. The im­age is a sec­tion of a glob­al to­po­graph­ic map of Mars; blue and green are low-ly­ing ar­eas, yel­low and red are el­e­vat­ed ter­rain. The im­age is about 5000 kilo­me­tres wide.
InSight brake parachute during a test
In­Sight brake parachute dur­ing a test
Image 4/8, Credit: NASA/JPL-Caltech/Lockheed Martin

InSight brake parachute during a test

The In­Sight brake parachute opens at the su­per­son­ic speed of 1500 kilo­me­tres per hour. The ini­tial load on de­ploy­ment at an al­ti­tude of 12 kilo­me­tres is 55,600 New­ton. Bare­ly three min­utes lat­er, 1200 me­tres above the land­ing site, the probe will sep­a­rate from the parachute and use its de­scent en­gines to de­cel­er­ate un­til land­ing at around 20:53 CET. The pic­ture shows the su­per­son­ic parachute at Lock­heed-Mar­tin in Den­ver, Col­orado dur­ing a test.
Artist’s impression of the NASA InSight lander on the Martian surface
Artist’s im­pres­sion of the NASA In­Sight lan­der on the Mar­tian sur­face
Image 5/8, Credit: NASA/JPL-Caltech.

Artist’s impression of the NASA InSight lander on the Martian surface

Launched on 5 May 2018, NASA’s In­Sight space­craft will land on 26 Novem­ber, just north of the Mar­tian equa­tor, and de­ploy its so­lar pan­els. SEIS, an in­stru­ment for record­ing seis­mic waves (left of im­age), and HP³, an in­stru­ment de­vel­oped by DLR to mea­sure the ther­mal con­duc­tiv­i­ty of the Mar­tian re­golith and the heat flow from the in­te­ri­or of the plan­et (right of im­age), will be placed on the sur­face of the plan­et pos­si­bly be­fore the turn of the year.
Instruments and technical components of InSight
In­stru­ments and tech­ni­cal com­po­nents of In­Sight
Image 6/8, Credit: NASA/JPL-Caltech.

Instruments and technical components of InSight

In­Sight’s struc­tural de­sign is sim­i­lar to that of NASA’s Phoenix lan­der from 2008. The main com­po­nent is a plat­form two me­tres in di­am­e­ter, on which most of the sys­tem com­po­nents – the ex­per­i­ments in their ‘trans­port mode’, the an­ten­nas, the on-board com­put­er, the thrusters, the pro­pel­lant tanks and three tele­scop­ic legs are at­tached. A robot­ic arm will be de­ployed af­ter land­ing and lift the ex­per­i­ments HP3 and SEIS from the plat­form on­to the Mar­tian sur­face. At the side of the plat­form are two so­lar pan­els, which pro­duce a max­i­mum of 700 watts, de­pend­ing on the dis­tance be­tween Mars and the Sun. The RISE ex­per­i­ment is con­duct­ed from the plat­form it­self.
Components of HP3
The HP³ ex­per­i­ment
Image 7/8, Credit: NASA/JPL; DLR.

The HP³ experiment

DLR has con­tribut­ed the HP³ ex­per­i­ment to the NASA In­Sight mis­sion. HP³ stands for ‘Heat Flow and Phys­i­cal Prop­er­ties Pack­age’ and the in­stru­ment was de­vel­oped un­der the lead­er­ship of the DLR In­sti­tute of Plan­e­tary Re­search. The ther­mal con­duc­tiv­i­ty of the ma­te­ri­al be­low the land­ing site and the heat flow from the in­te­ri­or of Mars to the sur­face will be mea­sured us­ing a pen­etrom­e­ter ham­mered five me­tres deep in­to the Mar­tian re­golith. The ex­per­i­ment is de­signed for an op­er­a­tional life of two Earth years. Es­sen­tial com­po­nents of HP3 are the ‘Mole’ and the rib­bon ca­ble with the tem­per­a­ture sen­sors, which the Mole will pull be­hind it in­to the ground to per­form mea­sure­ments.
Internal structure of Mars
What is the in­te­ri­or of Mars like?
Image 8/8, Credit: JPL/NASA

What is the interior of Mars like?

The In­Sight mis­sion will in­ves­ti­gate the in­ter­nal struc­ture of Mars and the pro­cess­es at play in­side the plan­et to ac­quire a bet­ter un­der­stand­ing of the for­ma­tion and evo­lu­tion of earth-like plan­ets. Sim­i­lar to the oth­er ter­res­tri­al plan­ets – Mer­cury, Venus, Earth and the Moon – Mars has a metal­lic core sur­round­ed by a rocky man­tle, over which lies a rocky crust. Ac­cord­ing to mod­el cal­cu­la­tions, the core has a tem­per­a­ture of about 1900 de­grees Cel­sius and could still be molten if it con­tains a sig­nif­i­cant amount of sul­phur. This is one of the ques­tions that the In­Sight mis­sion will ad­dress. The mis­sion will al­so con­duct a study of seis­mic ac­tiv­i­ty and mea­sure the me­te­orite im­pact rate on Mars.
  • Exploring Mars' interior - To date, the structure of Mars and the size and condition of its core are only vaguely known.
  • The mission with the DLR experiment HP3 (Heat Flow and Physical Properties Package) will provide new insights on how Mars' interior and rocky planets like Earth have evolved.
  • The landing on Mars is scheduled for 26 November 2018.
  • Focus: Space, exploration

It will be the deepest hole ever hammered into another celestial body using manmade technology. During the NASA InSight mission, the Heat Flow and Physical Properties Package (HP3), the Mole, which was developed and built by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) will penetrate up to five metres deep into the Martian soil to measure the temperature and thermal conductivity of the substrate materials there. This glimpse of the interior of the Red Planet will help us to better understand the formation and evolution of Earth-like bodies. The landing is scheduled to take place at 20:53 CET on 26 November 2018 on the Elysium Planitia plain, a bit north of the Martian equator. As the hour approaches, excitement is mounting over where exactly the landing probe will touch down within the 140-kilometre-long landing ellipse and where an appropriate spot for the historic Mars experiment might be found at the landing site. Until now, heat flow measurements have only been performed on the Moon, as part of the Apollo 17 mission, during which the astronauts Eugene Cernan and Jack Schmitt used a hand-powered drill to bore up to three metres into the surface.

"Our Mars mole is doing well on board InSight on its final stretch to Mars," says the Principal Investigator of the HP3 experiment, Tilman Spohn of the DLR Institute of Planetary Research in Berlin. "Checks during the cruise phase did not reveal any irregularities. Now we are eagerly yet confidently awaiting the landing just a few days from now."

Spohn and a number of other DLR scientists will be at the Jet Propulsion Laboratory (JPL) on 26 November, which runs the mission for NASA. Also present will be scientists from the DLR Microgravity User Support Center in Cologne (MUSC), which is directly involved with the mission operations team that is controlling the mole. "From the landing and the choice of a definitive site on the surface all the way through to the successful penetration of the Martian soil, we will be working directly with our US colleagues at the control centre in Pasadena, California," says HP3 Operations Manager Christian Krause.

The deployment of the HP3 experiment is now planned for early January 2019. At this point, the penetrometer will gradually hammer down to a depth of five metres in 50-centimetre progressions over three phases that will be repeatedly interrupted by measurements and checks. It will use a fully automatic electrically powered hammer mechanism and pull a tether fitted with measuring sensors behind it along into the Martian soil. "As we do not know what surprises – hard rocks, for instance – may await us underground, we will proceed with great caution and are planning to reach our target depth within several weeks, in March 2019," adds Spohn. Another part of the HP3 experiment involves an infrared radiometer, which will be activated shortly after the landing and will measure the surface thermal radiation yielding the temperature of Mars from the lander platform. Together, these datasets will make it possible to draw conclusions about the planet's heat flow.

Landing in a 'car park'

In order to mitigate the risks to the mission, the engineers and scientists have chosen a landing area southwest of the large Elysium volcanic complex, on the Elysium Planitia plain, which is largely flat and free of large stones and rocks. The deliberate monotony of this landing site, essential for conducting measurements beneath the surface of Mars, has led NASA researchers to describe the landing, in tongue-in-cheek fashion, as taking place on a large 'parking lot'. Yet even here, precise analysis of landing site will be necessary from the very start. Once this has been done, a robotic arm will set the seismometer SEIS (Seismic Experiment for Interior Structure), built under the lead of CNES by an international consortium to which DLR has also contributed, down on the surface. The seismometer will record waves that originate from marsquakes and meteorite impacts and propagate through the planet. As a next step, the HP3'Mole' experiment, which was developed and built at DLR, will be placed on the surface. The InSight landing platform also carries the US experiment RISE (Rotation and Interior Structure Experiment), which will record fluctuations in the Mars' rotation axis.

Braking manoeuvre at 1500 degrees Celsius

Before the measurements can begin, InSight must first endure the roughly seven-minute critical Entry, Descent and Landing phase (EDL). On 26 November 2018 at 20:47 CET, the probe will enter the Martian atmosphere at a shallow angle. In the process, the protective shield will heat up to around 1500 degrees Celsius within three minutes. The friction with the Martian atmosphere will slow down the probe until a parachute opens 12 kilometres above the ground, allowing the lander to slowly float down to the planet's surface. Upon separation from the parachute at an altitude of 1200 metres, InSight will be decelerated by its descent engines. Contact will be maintained with the space probe during its flight to Mars and over the course of the mission via the 70-metre antennas of NASA's Deep Space Network in California, Australia and Spain. The NASA Mars Reconnaissance Orbiter and Mars Odyssey 2001 probes will fly over the InSight landing site twice per Martian day and will serve as relay stations for communications with Earth.

Looking at Mars to discover how Earth was formed

InSight is a stationary geophysical observatory, and the only one of its kind in the history of Solar System research. Its main scientific task is to investigate the interior and composition of our neighbouring planet, examining the evolution, structure and physical properties of the crust, mantle and core, thus enabling us to draw conclusions about the formation and evolution of terrestrial bodies. Mars is the perfect destination, as it is relatively easy to reach and makes an ideal comparison object to Earth.

The processes that took place after the formation of a metal core inside Mars and in the overlying rock mantle and crust likely slowed down faster than they did on Earth. As such, the fingerprints of the processes that once formed the core, mantle and crust of Earth-like planets may have been better preserved on Mars to this day. Researchers are thus hoping to gain a deeper understanding of what occurred from the formation of Earth up to the evolution of life, also comparing these processes with those that occurred on its closest neighbours, Mercury, Venus and Mars, as well as looking at rocky planets orbiting other stars. The researchers are curious as to whether there is still a hot, molten core at the centre of Mars – as there is on Earth – and whether this is completely molten, unlike on Earth, as some theories suggest. Tilman Spohn, who developed this theory together with fellow scientists from the US in the 1990s, maintains that "This model would easily explain the lack of a magnetic field on Mars today".

The HP3 experiment on the NASA InSight mission

The InSight mission is being conducted by the Jet Propulsion Laboratory (JPL) in Pasadena, California, on behalf of NASA's Science Mission Directorate. The InSight mission is part of the NASA Discovery Program. DLR is contributing to the mission with its HP3 (Heat Flow and Physical Properties Package) experiment. The DLR Institute of Planetary Research, which was responsible for developing the experiment in collaboration with the DLR institutes of Space Systems, Optical Sensor Systems, Space Operations and Astronaut Training, Composite Structures and Adaptive Systems, System Dynamics and Control, and Robotics and Mechatronics, is leading the experiment. The industry partners Astronika, CBK Space Research Centre, Magson and Sonaca are also involved. The Space Research Institute at the Austrian Academy of Science and the University of Kaiserslautern are scientific partners for the project. HP3 is operated by the DLR Microgravity User Support Centre (MUSC) in Cologne.

Detailed information on InSight and the HP3 experiment are available on DLR's dedicated mission site: www.dlr.de/en/insight. For mission updates follow @NASAInSight on Twitter.

Contact
  • Falk Dambowsky
    Ed­i­tor
    Ger­man Aerospace Cen­ter (DLR)
    Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Fax: +49 2203 601-3249
    Linder Höhe
    51147 Cologne
    Contact
  • Matthias Grott
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    HP³ project sci­en­tist and In­Sight sci­ence team mem­ber; Fo­cus on heat flow and ther­mal con­duc­tiv­i­ty mea­sure­ments; In­stru­ment de­vel­op­ment
    Rutherfordstraße 2
    12489 Berlin
    Contact
  • Olaf Krömer
    Ger­man Aerospace Cen­ter (DLR)

    DLR In­sti­tute of Space Sys­tems
    Telephone: +49 421 24420-1138
    Linder Höhe
    51147 Köln
    Contact
  • Dr.-Ing. Björn Timo Kletz
    Ger­man Aerospace Cen­ter (DLR)

    DLR In­sti­tute of Com­pos­ite Struc­tures and Adap­tive Sys­tems
    Telephone: +49 531 295-3228
    Fax: +49 531 295-2876
    Lilienthalplatz 7
    38108 Braunschweig
    Contact
  • Prof.Dr. Tilman Spohn
    HP³ Prin­ci­pal In­ves­ti­ga­tor
    Ger­man Aerospace Cen­ter (DLR)

    DLR In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-300
    Fax: +49 30 67055-303
    Linder Höhe
    51147 Köln
    Contact
  • Martin Knapmeyer
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-394
    Rutherfordstraße 2
    12489 Berlin
    Contact
  • Dr Anko Börner
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Op­ti­cal Sen­sor Sys­tems
    In­sti­tute of Op­ti­cal Sen­sor Sys­tems
    Telephone: +49 30 67055-509
    Rutherfordstraße 2
    12489 Berlin-Adlershof

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