Philae (spacecraft)

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Philae
Philae model
Life-size model of Philae
Mission type Comet lander
Operator European Space Agency
COSPAR ID PHILAE
Website www.esa.int/rosetta
Mission duration 1–6 weeks (planned)
Spacecraft properties
Launch mass 100 kg (220 lb)
Payload mass 21 kg (46 lb)
Dimensions 1 × 1 × 0.8 m (3.3 × 3.3 × 2.6 ft)[1]
Power 32 watts at 3 AU[2]
Start of mission
Launch date 2 March 2004, 07:17 (2004-03-02UTC07:17Z) UTC
Rocket Ariane 5G+ V-158
Launch site Kourou ELA-3
Contractor Arianespace
67P/Churyumov–Gerasimenko lander
Landing date November 2014 (planned)
Instruments
APX Alpha: Alpha Proton X-ray Spectrometer
ÇIVA: Comet nucleus Infrared and Visible Analyzer
CONSERT COmet Nucleus Sounding Experiment by Radiowave Transmission
COSAC: COmetary SAmpling and Composition
MUPUS: Multi-Purpose Sensors for Surface and Subsurface Science
PTOLEMY: gas chromatograph and medium resolution mass spectrometer
ROLIS: ROsetta Lander Imaging System
ROMAP: ROsetta lander MAgnetometer and Plasma monitor
SD2: Sample and Distribution Device
SESAME: Surface Electric Sounding and Acoustic Monitoring Experiment

Philae is a robotic European Space Agency lander that accompanies the Rosetta spacecraft. It is designed to land on comet 67P/Churyumov–Gerasimenko shortly after arrival in 2014.[3][4][5] The lander is named after Philae island in the Nile, where an obelisk was found that was used along with the Rosetta Stone to decipher Egyptian hieroglyphic.

Design[edit]

The lander is designed to touch down on the comet's surface after detaching itself from the main spacecraft body and "falling" towards the comet along a ballistic trajectory. It also will deploy harpoons to anchor itself to the surface, and the legs are designed to dampen the initial impact to avoid bouncing. Communications with Earth will use the orbiter spacecraft as a relay station to reduce the electrical power needed. The mission duration on the surface is planned to be at least one week, but an extended mission lasting months is possible.

The main structure of the lander is made from carbon fiber, shaped into a plate maintaining mechanical stability, a platform for the science instruments, and a hexagonal "sandwich" to connect all the parts. The total mass is about 100 kilograms (220 lb). Its "hood" is covered with solar cells for power generation.[6]

It was originally planned to rendezvous with the comet 46P/Wirtanen. A failure in a previous Ariane 5 launch vehicle closed the window to reach the comet. It necessitated a change in target to the comet 67P/Churyumov–Gerasimenko. The larger comet mass and the resulting increased impact velocity made modification of the landing gear necessary. Besides the changes made to launch time and target, the mission profile remained unchanged.[3]

Instruments[edit]

The science payload of the lander consists of ten instruments massing 26.7 kilograms (59 lb), making up nearly one third of the mass of the lander.[7]

  • APXS (Alpha Proton X-ray Spectrometer) APXS analyzes the chemical element composition of the surface below the lander. The instrument is an improved version of the APXS of the Mars Pathfinder.
  • COSAC (The COmetary SAmpling and Composition) The combined gas chromatograph and time of flight mass spectrometry will perform analysis of soil samples and determine the content of volatile components.[8]
  • Ptolemy[9][10]
  • ÇIVA (Comet Nucleus Infrared and Visible Analyzer)
  • ROLIS (Rosetta Lander Imaging System)
  • CONSERT (COmet Nucleus Sounding Experiment by Radiowave Transmission). The CONSERT radar will perform the tomography of the nucleus by measuring electromagnetic wave propagation from Philae and Rosetta throughout the comet nucleus in order to determine its internal structures and to deduce information on its composition.[11]
  • MUPUS (MUlti-PUrpose Sensors for Surface and Sub-Surface Science)
  • ROMAP (Rosetta Lander Magnetometer and Plasma Monitor)
  • SESAME (Surface Electric Sounding and Acoustic Monitoring Experiment)[12]
  • SD2 (The sampling, drilling and distribution subsystem)

Mission[edit]

Landing gear pads and the ice screw at the end of the lander legs.

Philae's mission is to land successfully on the surface of a comet, and transmit data from the surface about the comet's composition. Unlike the Deep Impact probe, it is not an impactor. A check of the instruments indicated no major problems in 2006.[13] Some of the instruments and the lander were used for the first time as autonomous systems during the Mars flyby on 25 February 2007. ÇIVA, the camera system, returned some images while the Rosetta instruments were powered down; ROMAP took measurements of the Martian magnetosphere. Most of the other instruments need contact with the surface for analysis and stayed offline during the flyby.

International Contribution[edit]

Austria 
The Austrian Space Research Institute developed the lander's anchor and two sensors within MUPUS, which are integrated into the anchor tips. They indicate the temperature variations and the shock acceleration.
Finland 
The Finnish Meteorological Institute provided the Memory of the Command, Data and Management System(CDMS) and the Permittivity Probe (PP).
France 
The French Space Agency together with some scientific laboratories (IAS, SA, LPG, LISA) provided the system's overall engineering, radiocommunications and battery assembly, CONSERT, CIVA and the ground segment (overall engineering and development/operation of the Scientific Operation & Navigation Centre).
Germany 
The German Space Agency (DLR) has provided the structure, thermal subsystem, flywheel, the Active Descent System(procured by DLR but made in Switzerland), ROLIS, downward-looking camera, SESAME, acoustic sounding and seismic instrument for Philae. It has also managed the project and did the level product assurance. The University of Münster built MUPUS (it was designed and built in Space Research Centre of Polish Academy of Sciences [14]) and the University of Braunschweig the ROMAP instrument. Max Planck Institute for Solar System Research made the payload engineering, eject mechanism, landing gear, anchoring harpoon, central computer, COSAC, APXS and other subsystems.
Hungary 
The Command and Data Management Subsystem (CDMS) designed in the Wigner Research Centre for Physics of the Hungarian Academy of Sciences. The Power Subsystem (PSS) designed in the Department of Broadband Infocommunications and Electromagnetic Theory at Budapest University of Technology and Economics. CDMS is the fault tolerant central computer of the lander, while PSS assures that the power coming from the batteries and solar arrays are properly handled, controls battery charging and manages the onboard power distribution.
Italy 
The Italian Space Agency has a significant role in Philae. It has provided the SD2 instrument and the Photo Voltaic Assembly. The industrial contractors are respectively Tecnospazio spA and Galileo Avionica spA.
Ireland 
Space Technology Ireland Ltd. has designed, constructed and tested the Electrical Support System Processor Unit (ESS) for the Rosetta mission. ESS stores, transmits and provides decoding for the command streams passing from the spacecraft to the lander and handles the data streams coming back from the scientific experiments on the lander to the spacecraft.
Poland 
The Space Research Centre of Polish Academy of Sciences built MUPUS.[14]
United Kingdom 
The Open University and the Rutherford Appleton Laboratory (RAL) have developed PTOLEMY. RAL has also constructed the blankets that keep the lander warm throughout its mission. Surrey Satellites Technology Ltd. (SSTL) constructed the momentum wheel for the lander. It stabilises the module during the descent and landing phases.

References[edit]

  1. ^ "PHILAE". National Space Science Data Center. Retrieved 28 January 2014. 
  2. ^ "Philae lander fact sheet". DLR. Retrieved 28 January 2014. 
  3. ^ a b S. Ulamec, S. Espinasse, B. Feuerbacher, M. Hilchenbach, D. Moura, H. Rosenbauer, H. Scheuerle, R. Willnecker (2006). "Rosetta Lander—Philae: Implications of an alternative mission". Acta Astronautica 58 (8): 435–441. Bibcode:2006AcAau..58..435U. doi:10.1016/j.actaastro.2005.12.009. 
  4. ^ J. Biele (2002). "The Experiments Onboard the ROSETTA Lander". Journal Earth, Moon, and Planets 90 (1–4): 445–458. Bibcode:2002EM&P...90..445B. doi:10.1023/A:1021523227314. 
  5. ^ Agle, DC; Cook, Jia-Rui; Brown, Dwayne; Bauer, Markus (17 January 2014). "NASA Release = 2014-015 - Rosetta: To Chase a Comet". NASA. Retrieved 18 January 2014. 
  6. ^ Biele, Jens (2002). Earth Moon and Planets 90: 445. Bibcode:2002EM&P...90..445B. doi:10.1023/A:1021523227314. 
  7. ^ Bibring, J.-P.; Rosenbauer, H.; Böhnhardt, H.; Ulamec, S.; Biele, J.; Espinasse, S.; Feuerbacher, B.; Gaudon, P.; Hemmerich, P. (2007). "The Rosetta Lander ("Philae") Investigations". Space Science Reviews 128: 205. Bibcode:2007SSRv..128..205B. doi:10.1007/s11214-006-9138-2. 
  8. ^ Goesmann F., Rosenbauer H., Roll R., Böhnhardt H. (2005). "COSAC onboard Rosetta: A bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko". Astrobiology 5 (5): 622–631. Bibcode:2005AsBio...5..622G. doi:10.1089/ast.2005.5.622. PMID 16225435. 
  9. ^ Wright, I. P.; Barber, S. J.; Morgan, G. H.; Morse, A. D.; Sheridan, S.; Andrews, D. J.; Maynard, J.; Yau, D.; Evans, S. T.; Leese, M. R.; Zarnecki, J. C.; Kent, B. J.; Waltham, N. R.; Whalley, M. S.; Heys, S.; Drummond, D. L.; Edeson, R. L.; Sawyer, E. C.; Turner, R. F.; Pillinger, C. T. (2006). "Ptolemy – an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus". Space Science Reviews 128: 363. Bibcode:2007SSRv..128..363W. doi:10.1007/s11214-006-9001-5. 
  10. ^ D. J. Andrews, S. J. Barber, A. D. Morse, S. Sheridan, I. P. Wright, G. H. Morgan (2006). "Ptolemy: An Instrument aboard the Rosetta Lander Philae, to Unlock the Secrets of the Solar System". Lunar and Planetary Science. XXXVII: 1937. 
  11. ^ Kofman, W., A. Herique, J-P. Goutail, T. Hagfors, I. P. Williams, E. Nielsen, J-P. Barriot, Y. Barbin, C.Elachi, P. Edenhofer, A-C. Levasseur-Regourd, D. Plettemeier, G. Picardi, R. Seu, V. Svedhem (2007). "The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT). A short description of the instrument and of the commissioning stages". Space Science Reviews 128: 413–432. Bibcode:2007SSRv..128..413K. doi:10.1007/s11214-006-9034-9. 
  12. ^ Seidensticker, K. J.; Möhlmann, D.; Apathy, I.; Schmidt, W.; Thiel, K.; Arnold, W.; Fischer, H.-H.; Kretschmer, M.; Madlener, D. (2007). "Sesame – An Experiment of the Rosetta Lander Philae: Objectives and General Design". Space Science Reviews 128: 301. Bibcode:2007SSRv..128..301S. doi:10.1007/s11214-006-9118-6. 
  13. ^ Biele, J; Willnecker, R; Bibring, J.-P.; Rosenbauer, H (2006). "Philae (Rosetta Lander): Experiment status after commissioning". Advances in Space Research 38 (9): 2025. Bibcode:2006AdSpR..38.2025T. doi:10.1016/j.asr.2006.09.016. 
  14. ^ a b http://mechatronics.cbk.waw.pl/en/projects/the-mupus-instrument-for-rosetta-mission-to-comet-churyumov-gerasimenko

External links[edit]