Ni. Komle et al., USING THE ANCHORING DEVICE OF A COMET LANDER TO DETERMINE SURFACE MECHANICAL-PROPERTIES, Planetary and space science, 45(12), 1997, pp. 1515
Owning to the low surface gravity of the Rosetta target comet 46P/Wirt
anen, a means of anchoring the Rosetta Lander to the cometary surface
will be necessary. This task can be accomplished by firing an anchor i
nto the cometary soil immediately after touchdown to prevent a rebound
of the spacecraft from the surface or subsequent ejection by other fo
rces, and to allow for mechanical activities (drilling, etc.) at the l
anding site. The rational for anchoring is examined, based on estimate
s of the main forces likely to act on the spacecraft after landing. We
report on the development of an anchoring device using a pyrotechnic
gas generator as a power source and an instrumented anchor. In additio
n to the anchoring function, which is the primary purpose of this syst
em, the integration of acceleration and temperature sensors into the t
ip offers the possibility to determine some important material propert
ies of the cometary surface layer. The accelerometer is designed to me
asure the deceleration history of the projectile and is thus expected
to give information on how the material properties (in particular stre
ngth) change within the penetrated layer(s), while the temperature sen
sor will measure temperature variations at the depth at which the anch
or finally comes to rest. As the mechanical properties of the material
are not known, it is difficult to predict the final depth of the anch
or with any great certainty, but it may well be greater than that reac
hed by any other of the lander's instruments. The instrumented anchor
will be part of the MUPUS experiment, selected to form part of the Ros
etta Lander payload. We report on results of laboratory simulations of
anchor penetration performed at the Institut fur Weltraumforschung, G
raz, and compare these with models of projectile penetration. The valu
e of the results expected from the penetrometry experiment in the cont
ext of an improved understanding of cometary processes is discussed. (
C) 1998 Elsevier Science Ltd. All rights reserved.