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

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)

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

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

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

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

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.

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

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

Comparison of the MCD with available data.

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.

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

MY27

Density 50°S<lat<50°N

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

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

Density vs season z = 70km Latitude < 50°

SPICAM vs GCM density z = 70km Obs

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

SPICAM vs GCM density z = 100km Obs

SPICAM vs GCM density z = 120km Obs

SPICAM vs GCM density with various « dust scenarios

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

Exploring the Mars Upper Atmosphere With Aerobraking Accelerometers Aerobraking Spacecraft Vertical Structures Seasonal (Ls) Coverage F10.7 (at Earth) MGS1 (1997-1998) 7-months 400 (~115-160 km) 180-300 70-90 (MIN) MGS2 (1998-1999) 4.5-months 1200 (~110-160 km) 30-95 130-150 (MOD) Odyssey (2001-2002) ~3-months 650 (~95-150 km) 260-310 ~175-200 (MAX) MRO (2006) 5-months 900 (~95-170 km) 35-109 80-100

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

MCD: mean outputs Mars Odyssey data

MCD: mean outputs Mars Odyssey data

MCD: perturbed outputs Mars Odyssey data

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

Analysis of variability: MGS phase 2

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

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°

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 !

Forbes et al. 2002

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.

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

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

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

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

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

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 ?

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

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