1. Using the Mars climate Database for aerobraking (100-150 km)
François Forget
Laboratoire de Météorologie Dynamique, CNRS
06/04/2011

2. Background: LMD GCM simulation of the atmosphere thermosphere 0 – 300 km … . (F. Gonzalez-Galindo , M. Angelats I Coll, F. Forget, LMD) (see Gonzalez-Galindo et al., JGR, 2009a, 2009b, 2010)
Thermosphere parametrisation
Heating and cooling :
EUV heating NLTE cooling
Molecular conduction
Non Homogeneous atmosphere
Molecular diffusion
Photochemistry (21 reactions)
Species :
CO2, CO, O2,, H2 , O(3P), O(1D),, OH, H, HO2, H2O, H2O2, O3 , N2, Ar
Molecular
Conduction
EUV
IR (CO2) NIR (CO2)

3. Zonal mean Heating rates
Ls=270° (N. winter solstice)
NIR UV
Cond
15 µm

4. Introduction: Source of variability for the upper atmosphere density
Dust storm in the lower atmosphere
(impact temperature between 0 and ~60km, and thus density above)
Solar EUV variability
Atmospheric waves
Thermal tides (migrating and non migrating)
Transient waves
Gravity waves

5. Impact of dust storms : Mars Global surveyor aerobraking phase 1 detect a large regional storm “Noachis dust storm”
Keating et al. Science 1998

6. Introduction: Source of variability for the upper atmosphere density
Dust storm in the lower atmosphere
(impact temperature between 0 and ~60km, and thus density above)
Solar EUV variability
Atmospheric waves
Thermal tides (migrating and non migrating)
Transient waves
Gravity waves

7. Above ~120 km (thermosphere): Extreme UV heating varies with solar cycle (~11 years cycle, with flares)
The Extreme UV Solar Radio Flux depends on the solar activity, often characterized by the 10.7cm solar radio flux, easier to measure and predict.

8. Introduction: Source of variability for the upper atmosphere density
Dust storm in the lower atmosphere
(impact temperature between 0 and ~60km, and thus density above)
Solar EUV variability
Atmospheric waves
Thermal tides (migrating and non migrating)
Transient waves
Gravity waves

9. Mean characteristic of the simulated atmosphere and variability (LMD GCM) Exemple: Northern winter solstice

10. Comparison of the MCD with available data.

11. Very little data available between 80 and 150 km
Accelerometer data from previous aerobraking campaign (density)
CO2 density and temperature profile from UV stellar occultation using Spicam spectrometer on Mars Express.

12. Seasonal distribution of SPICAM stellar occultations (01/2004-03/2006)
Polar night
Subsolar point
Polar night

13. MY27

14. Density
50°S<lat<50°N

15. Unusual dust loading event around Ls=130° SPIRIT
Comparison with miniTES dust measurements from the Mars Exploration Rover
Smith et al. 2006
Unusual dust loading event around Ls=130°
SPIRIT
OPPORTUNITY
SPICAM

16. Density vs season z = 70km Latitude < 50° Ls =130°
Dusty lower atmosphere: +20K
Clear lower atmosphere
Ls =130°

17. Density vs season z = 70km
Latitude < 50°

18. SPICAM vs GCM density z = 70km
Obs

19. SPICAM vs GCM density z = 70km
Unusual dust loading
GCM ?
Obs

20. SPICAM vs GCM density z = 100km
Obs

21. SPICAM vs GCM density z = 120km
Obs

22. SPICAM vs GCM density with various « dust scenarios

23. Mean profile (S. winter)
SPICAM vs GCM density
Mean profile (S. winter)

24. Exploring the Mars Upper Atmosphere With Aerobraking Accelerometers
Aerobraking Spacecraft
Vertical
Structures
Seasonal
(Ls)
Coverage
F10.7
(at Earth)
MGS1
( )
7-months
400
(~ km)
70-90
(MIN)
MGS2
( )
4.5-months
1200
(~ km)
30-95
(MOD)
Odyssey
( )
~3-months
650
(~ km) ~
(MAX)
MRO
(2006)
5-months
900
(~ km)
35-109
80-100

25. Accelerometer Density Variations at 130 km (Keating et al., 2007)

26. MCD: mean outputs
Mars Odyssey data

27. MCD: mean outputs
Mars Odyssey data

28. MCD: perturbed outputs
Mars Odyssey data

29. Analysis of orbit to orbit variability Comparison of MCD data at fixed local time with MCD V4.3

30. Analysis of variability: MGS phase 2

31. Observations compared to MCD V3 predictions 1 (Angelats iColl et al

32. Observations compared to MCD V3 predictions 2 (Angelats iColl et al
LT = 16h and Ls ≈ 65°
LT = 15h and Ls ≈ 80°
LT = 15h and Ls ≈ 80°
LT = 15h and Ls ≈ 80°

33. Migrating tides : Wave directly forced by the sun  propagate westward
On Mars, the solar forcing interact with the topography and create “Non migrating tides”  they can propagate eastward !

34. Forbes et al. 2002

35. Summary : Mars main tidal modes
Definition: s is the zonal wavenumbers (s>0 westward s<0 eastward)
n is the period : n=1 is a diurnal period and n=2 is a semi-diurnal period)
Migrating tidal modes with the same phase speed as the Sun, westward
mostly s=1, n=1 (diurnal oscillation)
s=2 n=2 (semi diurnal oscillation)
Non-migrating tidal modes, with 3 major modes usually described:
n = 1 s = −1 (diurnal Kelvin wave “DK1”)
n = 1, s = −2 (diurnal Kelvin wave known as “DK2”)
n = 2, s = −1. (semi-diurnal Kelvin wave known as SK1)
Why are these eastward propagating waves so important ?
Because the atmosphere tend to resonate and amplify these waves
And because satellite on near polar orbit (~fixed local time) will mostly “see” the variability resulting from these modes with longitude.. In a fixed local time reference frame, DK1 causes wave-2 zonal variations and DK2 and SK1 cause wave-3 zonal variations. All three of these have been observed throughout the martian atmosphere.

36. Detailed analysis of MGS aerobraking measurements (LMD GCM, Angelats i coll et al., 2004)
Local time = 4pm
Observations
Mars Climate database (GCM)

37. MGS aerobraking in-situ density simulation: Analysis of the waves involved (Angelats i Coll et al. , 2003)
Wavenumber=3
Wavenumber=1
Wn =
Wavenumber=2

38. Impact of small scale waves (gravity waves
Impact of small scale waves (gravity waves ?) : Mars Odyssey, orbit 199 (Ls=302°)
- MCD (mean)
- Mars Odyssey data

39. Impact of small scale waves (gravity waves
Impact of small scale waves (gravity waves ?) : Mars Odyssey, orbit 199 (Ls=302°)
- MCD (perturbed with new seed)
- Mars Odyssey data

40. Impact of small scale waves (gravity waves
Impact of small scale waves (gravity waves ?) : Mars Odyssey, orbit 199 (Ls=302°)
- MCD (perturbed with new seed every 10S)
- Mars Odyssey data

41. Some general conclusions
MCD tend to overestimate density at aerobraking altitudes
Variability of density in the aerobraking ranges (100 – 150 km) is controlled by
Impact of local, regional, and global dust storms on the thermal structure below : MCD OK ?
Variability of EUV flux on the thermospheric temperature above ~120 km: MCD ~OK
Variation with local time, longitude and latitude of thermal tides planetary waves. MCD ~OK
Forcing at the surface and in-situ
Numerous harmonics superimposed
Non polar orbit will experienced the strong diurnal density cycle (migrating tides directly forced)
Poorly known day to day variability from transient (e.g. baroclinic waves), especially near the winter pole… MCD not validated
Possibly : small scale waves . MCD with perturbation: to be validated ?

42. Planned improvements for Mars Climate database v5 (collaboration with IAA, spain)
Improved thermal structure in the lower atmosphere…
Improved CO2 15-μm Thermal Cooling Rates
Taking into account predicted atomic Oxygen
Improved NLTE scheme
Improved Near-IR Solar Heating Rates
 Tuning and validation with SPICAM and aerobraking data + Ionospheric observations

43. ~120km
~90 km
~60 km
Forget et al. JGR 2009