Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmdi43a1945s&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #DI43A-1945
Physics
[5418] Planetary Sciences: Solid Surface Planets / Heat Flow, [6297] Planetary Sciences: Solar System Objects / Instruments And Techniques
Scientific paper
With only two successful heat flow measurements performed on the surface of the Moon to date, the thermal state of the Moon remains poorly constrained. Furthermore, measurements were taken close to the boundary of the Procellarum KREEP terraine, and the obtained values may not be representative for the bulk of the planet. For Mars, no heat flow measurement is yet available. Here we will present the Heat Flow and Physical Properties Package HP-cubed a self-penetrating, robotic heat flow probe. The instrument consists of electrical and temperature sensors that will be emplaced into the lunar subsurface by means of an electro-mechanical hammering mechanism. The instruement is foreseen to penetrate 3-5 m into the planet’s soil and will perform depth resolved measurements, from which the surface planetary heat flow can be directly deduced. The instrument has been pre-developed in two ESA funded precursor studies and has been further developed in the framework of ESA’s ExoMars mission. The current readiness level of the instrument is TRL 5.62 (ESA PDR Apr. 2009) which has been achieved with several Breadboards developed and tested between 2004 and 2009. As no drilling is required to achieve soil penetration, HP-cubed is a relatively lightweight heat flow probe, weighting less than 1800 g. It has been further studied as parts of the discovery proposals Lunette and GEMS and for the proposed Japanese lunar mission SELENE 2 The instrument consists of an electro-mechanic mole, a pay-load compartment, and a tether equipped with temperature sensors. The latter can be actively heated for thermal conductivity measurements. A tiltmeter and acceleraometer will help to track the path of the mole. The payload compartment has room for sensors such as a permittivity probe, a bore-hole camera, and/or a masspectrometer. Following deployment of the instrument, instrument operations will be split into two phases: During the penetration phase soil intrusion is achieved by means of the electro-mechanical hammering mechanism. The net hammering time is expected to be ~12 h to reach the final depth, but hammering will be interrupted at intervals of 0.5 m to conduct thermal conductivity and electrical measurements. After the final penetration depth has been reached, the instrument will switch to the monitoring mode. This mission phase basically consists of column temperature readings and lasts to the end of the mission. To determine the heat flow, the thermal gradient as well as the thermal conductivity of the regolith need to be determined. For the measurement approach persued here, the attainable accuracy for the thermal conductivity determination is 5 % and given an accuracy of the temperature sensors of 100 mK the accuracy of the thermal gradient determination is expected to be 7%. This implies an attainable accuracy of 7 % for the heat flow determination, which compares favourably to the uncertainty of 15 % given for the Apollo heat flow experiments.
Grott Matthias
Ho Tracey
Hudson Troy L.
Kargl Guenter
Smrekar Suzanne E.
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