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LMD1D v1 and v2 Comparison with Phoenix Flight Data

Prepared by Stéphane Lapensée

ESA-ESTEC, TEC-MTTKeplerlaan 1, 2201 AZ Noordwijk

The NetherlandsE-mail:  stephane.lapensee@esa.int

Tel.:   +31 (0)71.565.8733

TEC-MTT/2012/3788/In/SL

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Phoenix Landing Site Characteristic

• Based on Putzig 2007 thermal inertia maps, at the phoenix landing

sites the value varies from 92 to 575

– This is probably caused by the time/season when the

measurements where conducted. The surface ice may be causing

large variations.

• From the TES Albedo Maps, we can find a value of 0.19.

• Other Reference on thermal inertia maps can be found in the next

slide stating an Albedo of 0.21 and a thermal inertia of 250 to 283 for

the Phoenix landing site.

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Albedo and Thermal Inertia Mapping of Landing Site

Ref: Martian High latitude permafrost depth and surface-cover thermal inertia distribution: Josh Bandfield and al., 2008

Phoenix Landing Coordinates: 68.218830N 234.250778E, Landing Mars Solar Longitude (Ls)= 76.6. Mars Spring, May 25th 2008Albedo = 0.21, Thermal Inertia 250

Ref: RELATIONSHIPS BETWEEN REMOTE SENSING DATA AND SURFACE PROPERTIES OF MARSLANDING SITES. M. P. Golombek and al, 2009

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Phoenix Mission OD Measurements

• The following slide show the measured OD at the landing site during

the mission.

• There is an approximation made based on the figure since access to

numerical values is not possible.

– Greatest uncertainty is at the beginning of the mission, ie Sol 9

varies from 0.5 to 0.7

• Access to the numerical measurement values performed at every

mission Sol would reduce the uncertainty.

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Phoenix Landing Site Optical Depth Measurements

Ref: PHOENIX AND MRO COORDINATED ATMOSPHERIC SCIENCE. L. K. Tamppari et al., 2009

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Phoenix Temperature Measurements

• The Phoenix Lander is approximately 1m off the ground.

• The temperature measurements are at 0.25m, 0.5m and 1m from the deck.

– Measurements at 0.25 and 0.5m experienced perturbation from the lander

deck

– For comparison, the measurement performed at 1m is used.

• Hence total height is 2m from the ground

– There is mismatch of 1m in the comparison between LMD1D v1 and flight

data, since LMD1D v1 outputs data at 1m and Phoenix flight data are at

2m

– First comparison of LMD1D v2 to flight data was made using a height of 1m

in order to have a direct comparison with LMD1D v1.

– Following comparison of LMD1D v2 was made at 2m for one to one

comparison with flight data.

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Estimates of Environment Parameters tweaked for best fit with output of LMD1D v1

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Same Environmental Parameter but with comparison between LMD1D v1 and LMD1D v2 at 1m height but with flight data at 2m, SOL 9

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Same Environmental Parameter but with comparison between LMD1D v1 and LMD1D v2 at 1m height but with flight data at 2m, SOL 32

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Same Environmental Parameter but with comparison between LMD1D v1 and LMD1D v2 at 1m height but with flight data at 2m, SOL 119

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Same Environmental Parameter but with comparison between LMD1D v1 and LMD1D v2 at 1m height but with flight data at 2m, SOL 147

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LMD 1D v2 Validation using Phoenix Data

• The Flight measurement is estimated to be 2m from the ground. The

LMD 1D flux tool input was set to 2m

• It was found initially that very low Thermal inertia and high Albedo

was necessary to correlate with flight data.

– It was recommended to consider water ice at a depth of 5cm with

an inertia of 2000.

• As observed during the Phoenix Mission, clouds and ground fog

appeared mid way in the mission, Sol 60 – Sol 80. Their presence

affects the surface Albedo since they remained throughout the day as

the mission progressed in time. Hence, it may be necessary to

increase the Albedo in order to account for cloud presence.

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Tweaked Environmental Parameter for direct comparison with LMD1D v2 at 2m height and with flight data at 2m, SOL 9 and SOL 32

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Tweaked Environmental Parameter for direct comparison with LMD1D v2 at 2m height and with flight data at 2m, SOL 63 and SOL 84

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Tweaked Environmental Parameter for direct comparison with LMD1D v2 at 2m height and with flight data at 2m, SOL 119 and SOL 147

Note: Sol 119, problem correlating in early morning. Could be caused by instrument heat dissipation since they were doing night and early morning observations

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Conclusion

• For the comparison between the LMD1D v2 and flight data, the OD values were

adjusted but remained within the measurements range taking over several

days.

• The pressure values were measured with the flight pressure sensor

• The version 2 of LMD1D temperature profile fit better to the actual flight

measurement.

• We can observed from the flight measurement that the lander deck does affect

the measurements due to heat generated by the payloads as well as surface

finish of the lander deck

• The Albedo values used are within the TES measurement error except for Sol

147, which can be explained with the formation of ground fog and clouds. Sol

83 and 119 used a higher Albedo value in order to correlate, which is probably

due to Cloud formation.

• Thermal inertia values used are comparable to other references as long as sub-

surface ice at 5cm is considered in the input parameters.