Philae lander

Philae (previously known as RoLand) is the name of the lander that accompanies the Rosetta spacecraft. It is designed to land on comet 67P/Churyumov-Gerasimenko shortly after arrival. [cite journal | author= S. Ulameca, S. Espinasseb, B. Feuerbachera, M. Hilchenbachc, D. Mourad, H. Rosenbauerc, H. Scheuerlea, R.Willneckera | title=Rosetta Lander—Philae: Implications of an alternative mission | journal= Acta Astronautica | year=2006 | volume=58 | pages=435 – 441|doi=10.1016/j.actaastro.2005.12.009 ] [cite journal
author = J. Biele
title = The Experiments Onboard the ROSETTA Lander
journal = Journal Earth, Moon, and Planets
year = 2002
volume = 90
issue = 1-4
pages = 445–458
doi = 10.1023/A:1021523227314 ]

Design

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 weight is about 100 kg. Its “hood” is covered with solar cells for power generation.

The higher mass and therefore stronger gravitational force of the new target comet 67P/Churyumov-Gerasimenko compared to 46P/Wirtanen made changes in the landing gear necessary. [cite journal
author = Ulamec S, Espinasse S, Feuerbacher B, Hilchenbach M, Moura D, Rosenbauer H, Scheuerle H, Willnecker R
title = Rosetta Lander - Philae: Implications of an alternative mission
journal = Acta Astronautica
year = 2006
volume = 58
issue = 8
pages = 435–441
doi = 10.1016/j.actaastro.2005.12.009]

Instruments

*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. [cite journal
title = COSAC onboard Rosetta: A bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko
author = Gosmann F., Rosenbauer H., Roll R., Bohnhardt H.
journal = Astrobiology
volume = 5
issue = 5
pages = 622–631
year = 2005
doi = 10.1089/ast.2005.5.622]
*Ptolemy [cite journal
title = Ptolemy – an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus
author = 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.
journal = Space Science Reviews
volume = 128
issue = | pages = 363
year = 2006
doi = 10.1007/s11214-006-9001-5] [cite journal
title = Ptolemy: An Instrument aboard the Rosetta Lander Philae, to Unlock the Secrets of the Solar System
author = D. J. Andrews, S. J. Barber, A. D. Morse, S. Sheridan, I. P. Wright, G. H. Morgan,
journal = Lunar and Planetary Science
volume = XXXVII
issue =
pages = 1937
year = 2006
url = http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1937.pdf]
*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 the Rosetta probe throughout the comet nucleus in order to determine its internal structures and to deduce information on its composition. [cite journal|author= 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 |title= The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT). A short description of the instrument and of the commissioning stages |journal= Space Science Reviews |volume= 128 |pages=413–432 | year= 2007 | doi= 10.1007/s11214-006-9034-9]
*MUPUS (MUlti-PUrpose Sensors for Surface and Sub-Surface Science)
*ROMAP (Rosetta Lander Magnetometer and Plasma Monitor)
*SESAME (Surface Electrical, Seismic and Acoustic Monitoring Experiments)
*SD2 (The sampling, drilling and distribution subsystem)

Name

Philae is named for an island in the Nile river where an obelisk was found that was used to translate the Rosetta stone.

Mission

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. Some of the instruments and the lander were used for the first time as autonomous systems during the Mars flyby on February 25, 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.

External links

* [http://sci.esa.int/home/rosetta/ Rosetta website]
* [http://www.open.ac.uk/personalpages/a.j.ball/publications/online/capcom.html Rosetta Lander] an article by Andrew J Ball, 1997.
* [http://roland.mpae.gwdg.de/ Philae site] at gwdg.de
* [http://www.bernd-leitenberger.de/philae.shtml Experiments] German page with all onboard experiments.

References