A VERY HIGH RESOLUTION MARS CLIMATE MAPPER

1. Scientific Objectives The microwave sounder MAMBO aims to characterize the dynamics and the composition of the Martian atmosphere, with an unprecedented sensitivity. It will analyze the thermal emission of the atmosphere at microwave frequencies using heterodyne spectroscopy, for the first time from orbit around another planet. In practice, MAMBO will perform measurements at atmospheric limb and at nadir using a receiver dedicated to the monitoring of selected lines of key molecules in the range 320-350 GHz: H2O, CO, 13CO, HDO, O3, H2O2. The MAMBO instrument has been proposed for the CNES Premier Orbiter. Simulation performed with the MOLIERE optimal inversion scheme, Bordeaux Observatory (Baron,1999,Urban,2001) : because temperature sensitivity decreases with altitude, the MAMBO standard product for each limb scan (every 3° latitude) will typically include one temperature profile from 0 to 120 km with best vertical resolution of 5 km below 40 km. Δz = 13km Δz = 10 km Δz = 5km Electronics Unit Sensor and Receivers units • Photochemistry & Exobiology: • Hydrogen Peroxyde (H202): This species which is supposed to control H2, O2 and CO abundance and plays a major role on soil oxidisation has never been found on Mars. • Ozone : Ozone profile will be measured accurately up to 70 km, simultaneously with water vapour. This will allow us to better understand the relationship between the two species. • Carbon Monoxyde : the variations of this species will be monitored up to 120 km,providing important clues on the meridional transport in the Martian atmosphere. Simulated retrieval accuracy of minor species mixing ration for an observation time of 1s every 4km (red dash line) and 50s (red solid line) relative to expected concentration profiles (black lines) Expected variations of the [HDO]/[H2O] ratio at condensation level, as simulated by Bertaux and Montmessin (2002). The error bars illustrate the typical accuracy of MAMBO retrieval: thin error bars for 1 limb scan and thick error bars when averaging 50 profiles. MAMBO Mars Atmosphere Microwave Brightness Observer A VERY HIGH RESOLUTION MARS CLIMATE MAPPER F. Forget1, K. Dassas1, B. Thomas2, B. Germain2,3, M. Gheudin2, A.R. Deschamps2, G. Beaudin2, A. Maestrini2, T. Encrenaz4 , E. Lellouch4, C. Prigent2, P. Ricaud5 , J.Urban5, and, T. Clancy9, U. Frisk6, S. Gulkis8, P. Hartogh7, M.A. Janssen8 , (as main scientific partners representatives) 1 LMD, Paris, France 4LESIA, Observatoire de Paris, France 7 Max Planck Institut für Aeronomie (MPAE), Germany 2 LERMA, Observatoire de Paris, France 5L3AB, Bordeaux, France 8 Jet Propulsion Laboratory (JPL), Pasadena (CA), USA 3 SEGIME Ltd, Paris, France currently at LERMA 6 Swedish Space Centre (SSC), Stockolm, Sweden 9 Space Science Institute, USA Contact: francois.forget@lmd.jussieu.fr Limb z = 10 km Simulation of limb spectra around 320-350 GHz under typical martian conditions. • 3D Circulation • Wind: • Mambo will allow to retrieve the zonal wind at low latitudes. Limb viewing allows the first direct measurements of the winds on Mars from orbit from 20 to 110 km with a vertical resolution better than 10 km and an accuracy of about 15 m.s-1. Measurements will be especially interesting above 70 km, where no global measurements will be obtained until MAMBO. • Temperature: • The temperature will be retrieved simultaneously with the CO mixing ratio. • Microwave sounding allows to profile temperature with high vertical resolution (8 km) up to 120 km, compared to 70 km for previous other wavelength sounders. Instrument & Technology MAMBO design (courtesy of Astrium) is such that it fulfills scientific objectives totally independently of Orbiter configuration: MAMBO is thermally isolated from the Orbiter and mechanical and power inrterfaces are reduced to the minimum. MAMBO nominal position on Orbiter is towards nadir or on +Y/-Y sides along velocity vector. The MAMBO instrument is made of two heterodyne receivers at sub-millimeter wavelength, designed for continuum and spectroscopic detections in both polarizations . • A 23-cm Gregorian antenna performs cross-track field-of view observations. • A polarizing grid separates the signal into two orthogonal polarizations and directs them towards each receiver. • The low-noise heterodyne receivers are based on uncooled 330-GHz subharmonically pumped mixers using planar Schottky diodes technology. • A phase-locked ultra-stable oscillator is used to provide very high frequency stability for the spectroscopic measurements. • A set of spectrometers allows to observe both: • pressure-broadened spectral lines at 1–8 MHz resolution, and • atmospheric spectral lines at 100-kHz resolution. • The onboard computer will control housekeeping and scan mechanism and will monitore the 350-Mbits daily data rate. Above: A summary of the dynamical fields that will be observed by MAMBO, as simulated by a General Circulation Model (Forget, F. et al., J. Geophys. Res., 104, 24.155-24.176, 1999.) during Northern winter: temperature T and zonal wind U (eastward). The middle and right columns shows the expected RMS amplitude of key meteorological phenomena thought to create day to day variability (transient waves) and diurnal oscillations (thermal tides). Water Cycle: • Water vapour 3D mapping: • MAMBO will monitor the water vapour near the surface up to 60 km, with a sensitivity much better than previous experiments which gives the ability to retrieve vertical profiles dry atmospheres. Water vapour profile RMS retrieval accuracy for a typical atmospheric profile observed by MAMBO: 17 pr-µm column abundance. As for temperature,”over-sampling” the limb scanning allows to reach an effective resolution near 5km. However, the accuracy is better with a coarser resolution. • Data Processing, modelling • & Assimilation • The scientific analysis of the Data will be first based on the traditional production of the following data: • level 1 data: calibrated spectra, • level 2 data: e.g Wind, Temperature, mixing ratio profile, • level 3 data: climatology, average, maps, • level 4 data: assimilated data. • Two kinds of tools will be specifically developped for the operational data production: • A 1D retrieval model. • The employed retrieval method will be based on a state of the art ``Optimal Estimation`` scheme (Rodgers, 1976). Several teams may develop their own version, with a primary based at Bordeaux Observatory using the MOLIERE (Microwave Observations Line Estimation and Retrieval) tool originally developped to analyse the ODIN satellite aeronomy limb observations (Baron, 1999) • A data assimilation scheme: • This scheme will be used to determine the atmospheric circulation from the wind and temperature measurements. • D/H ratio: • This isotopic ratio will be mapped accurately from 0 to 40 km by simultaneous spectroscopy of H2O and HDO. Mapping the variation D/H ratio is a key investigation to understand the evolution of water on Mars, escape processes, and Mars cloud microphysics. Surface science: MAMBO will perform a dedicated mapping of the surface microwave emission and will map the variations due to: 1) subsurface ice contents 2) surface roughness 3) CO2 ice cap characteristic 4) temperature sensing depth . Emissivity polarization differences (V-H) on Earth at 85 GHz as observed by the SSM/I imager (Prigent et al. 1997). In the desert regions, this index is used to map the surface roughness. MAMBO will obtain similar data, for the entire planet. At 300 GHz, it should be sensitive to surface rugosity scale of the order of a few tens of meters.