Abstract
We describe the parameters that drive the design and modeling of the Rover Environmental Monitoring Station (REMS) Ground Temperature Sensor (GTS), an instrument aboard NASA’s Mars Science Laboratory, and report preliminary test results. REMS GTS is a lightweight, low-power, and low cost pyrometer for measuring the Martian surface kinematic temperature. The sensor’s main feature is its innovative design, based on a simple mechanical structure with no moving parts. It includes an in-flight calibration system that permits sensor recalibration when sensor sensitivity has been degraded by deposition of dust over the optics. This paper provides the first results of a GTS engineering model working in a Martian-like, extreme environment.
Highlights
NASA’s Mars Science Laboratory (MSL) is the first mission to include an environmental station, the Rover Environmental Monitoring Station (REMS), located on the Rover and with a mission duration of one Martian year to enable a study of Martian seasons [1,2]
The heat flux terms x are calculated using Planck’s law, where x refers to the body. These terms depend on the transmittance of the thermopile filter, bolometer absorbance, and the temperatures and emissivities of the different bodies, such as the thermopile case base (Tcb) and calibration plate (Tp), which can be directly measured using the specific Pt1000 temperature sensors, the thermopile bolometer (Ts) and thermopile case cap (Tcc), which are measured indirectly as will be described below, and thermopile filter (Tf), which is assumed to be equal to the temperature of the thermopile case cap since they are in good thermal contact
Using the data recorded for the 25th of January, Figure 10 shows the result of applying the Ground Temperature Sensor (GTS) measurement procedure; assuming that the thermopile filter is clean, this is = 1
Summary
NASA’s Mars Science Laboratory (MSL) is the first mission to include an environmental station, the Rover Environmental Monitoring Station (REMS), located on the Rover and with a mission duration of one Martian year to enable a study of Martian seasons [1,2]. In order to achieve high surface temperature accuracy, the value of soil emissivity must be estimated or measured This explains the need for specific studies of the IR reflectance properties associated with different kinds of Martian surface material such as minerals and rocks. The results obtained indicated significant percentage increases or decreases in reflectance over the entire wavelength range (e.g., basalt-hematite vs basalt-magnetite), and specific variations restricted to some spectral bands (e.g., basalt-smectite vs basalt-opal) Another alternative is the use of color pyrometry techniques [14,15] to estimate the emissivity value. Since emissivity is different to 1 and the surface reflectivity is assumed to be r = 1 − ε, IR solar radiation, as well as IR energy coming from the environment, mainly the Rover or lander and the atmosphere, augment ground emissions These factors must be taken into account and compensated if precise temperature estimation is required. - Needs at least two measuring bands and a very good estimation of atmospheric effects, so more complex than the standard contacless technique
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