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| Titel |
Determining the penetration resistance of a cometary surface by using data from the Philae anchoring harpoon |
| VerfasserIn |
Günter Kargl, Norbert I. Kömle, Wolfgang Macher |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097482
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| Publikation (Nr.) |
 EGU/EGU2014-13070.pdf |
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| Zusammenfassung |
| On November 11 2014 ESA’s Rosetta spacecraft will deliver the Lander PHILAE to the
surface of comet Churyumov-Gerasimenko. To fix the lander safely on the surface and allow
for in situ operation of instruments like the SD2 drill or the MUPUS experiment the
spacecraft will be anchored to the surface by a harpoon-type device. In addition to the
anchoring function the projectile shot into the surface contains two sensors, which will be
used to obtain information on the thermo-physical properties of the cometary ice: a shock
accelerometer and a temperature sensor. The former will record the deceleration history of
the anchoring projectile during the penetration phase. From these data information on
mechanical strength of the near surface cometary material and its variation with depth can be
retrieved by using appropriate modelling approaches. The temperature sensor will
measure temperature variations at the depth were the anchor finally has come to rest
over the lifetime of the lander at the surface. Both sensors are part of the MUPUS
experiment on Philae, which is devoted to the measurement of thermo-mechanical
properties.
In this paper we will give a short overview on the main features of the harpoon-anchoring
system in general and on the mathematical methods to be used for the evaluation of the
measurement data recorded by the anchor sensors, with emphasis on the accelerometer data.
An example from a test shot performed during the development phase of the Philae anchoring
system is shown in the figure below.
PIC
Figure: Typical acceleration/deceleration signal recorded during a test shot of the anchor
into a foam glass analogue material (upper left panel). The different phases of the shot
(acceleration phase, free flight phase, deceleration phase) are clearly separated in this shot.
Integration and double integration of the data (upper right and lower left panel) gives the
velocity and depth profile versus time. This procedure allows finally to derive the
acceleration/deceleration profile versus depth (lower right panel), which can be fed into a
material model to derive finally strength data like cohesion and angle of internal friction. |
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