Living with the Rosetta Lander Exploring a Comet with Philae Hermann Boehnhardt Max-Planck Institute for Solar System Research Göttingen, Germany Philae Mission, Amsterdam, May 2014 web source1 Orbiter & Lander Science - Ground Truth from Rosetta & Philae Orbiter instruments measure cometary properties from (remote sensing) or at (in-situ) a distance; they do not 'touch' the original cometary nucleus material and do not allow related laboratory-like experiments Lander instruments measure local properties of the nucleus and of the near-surface environment; the results have to be put in the global context for the comet as a whole ==> Orbiter and Lander results are partially self-constraining and partially complementary Philae Mission, Amsterdam, May 2014 2 Lander Contributions to Cometary Science How does the cometary activity work? Where are the sublimating ices? → Cameras, T sensors, gas and dust sensors, dielectric probe How does the surface morphology and structure look like on large to small scales? → Cameras What is the composition of the cometary material – gas & solids - at surface level? →Atomic element and molecular compounds (mass spectroscopy, alpha/X ray spectroscopy, visnir spectroscopy) What is the thermo-mechanical context on the surface and subsurface? → T sensors, accelerometers, acoustic detectors How does the cometary environment interact with the interplanetary one? → plasma & magnetic field sensors Philae Mission, Amsterdam, May 2014 3 The Philae Instruments web source Philae Mission, Amsterdam, May 2014 4 APXS Alpha & X ray spectrometer Elemental composition of Klingelhöfer surface (Univ. Mainz) CIVA Optical camera, microscope Imaging of landscape, structure Bibring camera and IR spectrometer & composition of samples (IAS Paris) CONSERT Radio sounder Dielectric properties of interior Kofman (lander) (Univ. Grenoble) COSAC Mass spectrograph, gas Molecular composition of Goesmann chromatograph samples and atmosphere, (MPS Göttingen) chirality MUPUS T sensors, accelerometers Physical properties of Spohn (hammer, harpoons) subsurface (density, porosity, (DLR Berlin) thermal properties) PTOLEMY Mass spectrograph, gas Isotopic composition of light Wright chromatograph elements in sample and (Univ. Milton atmosphere Keynes) ROLIS Optical down-looking camera Surface and grain imaging Mottola (DLR Berlin) ROMAP Magnetometer, plasma sensor Magnetic and plasma properties Auster (Univ. Braunschweig) SESAME Acoustic sensors, impact Electric and acoustic sounding, Seidensticker sensors, dielectric sensor dust grain properties (DLR Cologne) SD2 Drill Sample acquisition & transfer Finzi (Politec. Milano) Philae Mission, Amsterdam, May 2014 5 Comet – Sun Interaction ROMAP – magnetometer and plasma instrument Both instrument sensors measure modified solar wind parameters - modified due to presence of the comet and its activity Plasma sensors and magnetometer: at the nucleus a magnetic cavity may form with increasing activity level when the nucleus is approaching the Sun Measured physics: electron and ion flux distribution (density, energy, flow), magnetic field Science: 2nd example of a cometary environment free of solar plasma and magnetic field Philae Mission, Amsterdam, May 2014 web source 6 Magnetism and the Solar System Formation Magnetometer: during the descent local fields from magnetic material of the nucleus may influence the Romap sensor measurements ==> presence of local magnetized material Measured physics: magnetic field strength and orientation Science: magnetic interaction may have supported the agglomeration process or the early evolution of small bodies during the formation period of the solar system web source Philae Mission, Amsterdam, May 2014 7 Lab Science on the Comet PTOLEMY & COSAC - mass spectrometer & gas chromatographs Both instruments measure the local cometary gas atmosphere and the gas from pyrolized subsurface samples web source web source Philae Mission, Amsterdam, May 2014 8 The Link to Earth Ptolemy: Isotope determination for H, O, C, N Measurement: isotopic ratio of O atoms 16O/17O, 16O/18O and comparison with results from other bodies in the plaentary system Oxygen isotope ratios are tracer of the material mixing in primordial planetary disk Can the ocean water be of (partial) extraterrestrial origin? Philae Mission, Amsterdam,web May source 2014 web source 9 Organics in Comets COSAC: Determine organic compounds and their amount in the cometary material (volatile and non-volatile) The hints: - about two handful of organic species are known to exist in comets - about 1/3 of solid dust in comet Halley consisted of CHON compounds and may not evaporize under normal 'cometary conditions' - complex organics (polymers?) exist from Giotto flyby at Halley Did complex organics exist in planetary formation disk? GIOTTO Philae Mission, Amsterdam, May 2014 web source 10 Life Science on Comets Special organics: - Glycine (NH2CH2COOH) found in Stardust cometary grain - several amino acids in meteorites Measurement: content of amino acids and their chirality Is there a possible link with organics relevant for life on Earth? web source Philae Mission, Amsterdam, May 2014 11 Rosetta-Philae Combined Science Concert – an orbiter-lander instrument to look into the nucleus Radio sounding experiment: radio waves sent by the orbiter part, penetrate the surface and the nucleus; they are received by lander and are sent back to the orbiter again ==> pass twice through the surface layers and the whole nucleus ==> tomographic reconstruction of the surface layers and the nucleus interior Measured physics: dielectric constant of the material and of 'voids' Science: homogenuous vs heterogenuous structure <==> primordial vs evolved Philae Mission, Amsterdam, May 2014 web source 12 The Philae Spacecraft Passive lander web source Needs orbiter for release delivery and as relay station to Earth Spacecraft: Lander bus with subsystems for the landing & lander operations AND 10 scientific instruments Body: polygonal box with lander tripod web source (small refrigerator with 3 legs) ~1m height, ~2m foot print width Mass: 111kg (total) 26.7kg (payload) Named after flooded Philae islands in river Nile web source Philae Mission, Amsterdam, May 2014 13 How to Land Philae on a Comet? Philae is kept simple for the landing Only parts of the surface is within reach for Philae Orbiter flies special delivery trajectory for lander release It is 'thrown' at the comet (separation with 0.18-0.5 m/s) from a distance of about 2-3km above the surface web source During descent Z axis attitude stabilization by flywheel Energy absorption at touch-down through landing gear Anchoring through harpoons and ice screws Time to descend: 1h40min to several hours web source Philae Mission, Amsterdam, May 2014 14 Sequence of Events in the Philae Mission July- Oct. 2014 Landing site search and exploration by orbiter instruments 14 Sep. 2014 Landing site selection 12 Oct. 2014 Landing site confirmation 11 Nov. 2014 Separation, descent and landing of Philae 11-14 Nov. 2014 First Science Sequence of Philae mid Nov. - > Mar. 2015 Longterm Science Mission of Philae Thereafter Hope for more lander sciops opportunities Philae Mission, Amsterdam, May 2014 15 Risks and Challenges of the Philae Mission Spacecraft: Designed for a nucleus with a factor of ~40 less gravity ==> higher gravity acceleration, but landing gear for absorption of touch-down energy and momentum could not be adjusted Landing risks: Lateral speed at touch-down, a rough terrain or with a steep slope, a very hard or very soft surface ==> collision damages, turn-over, bouncing back or sinking into the ground Operations risks: Some units untested in flight (release mechanism, landing gear) ==> we will learn whether they work when we need them to work Environmental risks: Dust or ice coverage of solar panels Operations challenges: Power budget, orbiter-lander visibilities for RF link, cometary environment not as expected (this is almost for granted), compartment heating during approach to Sun Do you still think it is worthwhile to give it a try? We do so! Philae Mission, Amsterdam, May 2014 16 Who Built Philae and Who Performs the Lander Science? The Philae spacecraft is a independent contribution to the Rosetta mission provided by the lander consortium (ASI Italy, CNES+IAS France, ESA Europe, DLR Germany, FMI Finland, WIG Austria, KFKI Hungary, MPG Germany, UK Space, STIL Ireland) The lander instruments are provided by European research institutes through principle investigators and with support of national space agencies and research institutions The lander is operated from DLR (s/c & instrument ops), Cologne Germany, and CNES (sciops & data), Toulouse, France, within the Rosetta mission framework of ESA The costs and efforts for the Philae mission are: CTL 140 MEUR, CTC 180 MEUR, presently: ~ 60 scientists, ~ 60 engineers & technicians Philae Mission, Amsterdam, May 2014 17 Time is over …. Thank you for your attention Philae Mission, Amsterdam, May 2014 web source 18 Where to Find the Philae Landing Animation https://www.youtube.com/watch?v=siu2sxQ4YWI Philae Mission, Amsterdam, May 2014 19.