IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Status of the Indo-French Megha-Tropiques satellite project, perspectives for tropical systems studies Michel Desbois, Laurence Eymard, Rémy Roca, Nicolas Viltard, Michel Viollier, Michel Capderou with support of and

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Atmospheric energy budget in the intertropical zone and at system scale (radiation, latent heat, …)  Water budget of the systems (including precipitation and water vapor transport)  Conditions of appearance and development of these systems (Surface temperature, water vapor, winds,…)  Life cycle of Mesoscale Convective Complexes in the Tropics (over Oceans and Continents) Megha-Tropiques scientific objectives

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Megha-Tropiques additional objectives Operational aspects : assimilation for Cyclones, Monsoons, Mesoscale Convective Systems forecasting. (water vapour and precipitation) Contribution to climate monitoring : - Radiative budget (complementary to CERES) - Precipitation (enhanced sampling in the tropics) - Water vapour (tropical sampling)

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Frequent sampling of the intertropical zone measuring radiances related to : - Cloud properties and precipitation - Water vapor horizontal and vertical distribution - Outgoing radiative fluxes Association with operational satellites (geo and leo) Principles of the Megha-Tropiques Mission

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Coverage 23°N to 23°S, repetition time from 3 to 6 times per day à Tropical Orbit (20° inclination) à Wide Swath (altitude > 800 km) Study of Mesoscale convective systems > 100 km à Surface resolution from 10 to 40 km, depending on the parameter. Main Mission features

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Megha-Tropiques orbit

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October The three instruments of Megha-Tropiques ScaRaB : wide band instrument for inferring longwave and shortwage outgoing fluxes at the top of the atmosphere (cross track scanning, 40 km resolution at nadir) Saphir : microwave sounder for water vapour sounding : 6 channels in the WV absoption band at GHz. (cross track, 10 km) MADRAS : microwave imager for precipitation : channels at 18, 23, 37, 89 and 157 GHz, H and V polarisations. (conical swath, <10 km to 40 km)

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Position on the ISRO Platform

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October km 2300 km SAPHIR ScaRaB MADRAS Schematic representation of the swath of the 3 MT instruments

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Madras characteristics àColumn water vapor : 23 GHz àSea surface wind :18 GHz àPrecipitation, cloud water : 18, 23, 36.5, 89 GHz àActive convective areas, cloud ice : 89, 157 GHz àTwo polarisations required for all parameters, except column water vapor (23 GHz) àPrecipitation and cloud properties are best obtained from combination of channels. Proper combination requires identical field of views. This is specified for channels 18, 23, 36.5 GHz. àResolution at 89 GHz : 10 km with adjacent pixels, in order to get complete images of the active convective parts of the systems. à Resolution for lower frequencies will be lower (40 km) with oversampling in order to keep some information on smaller scales à157 GHz channel is an experimental channel intended to provide new information on ice at cloud top, eventually helping for precipitation estimation over land, and for lower layers WV retrieval. It will provide the best space resolution.

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October MADRAS specifications Channe l no. Central frequencies (GHz) Max. Bandwidth (MHz) Stability of frequency centre (MHz) NEDT (T°) sensitivity at 300K Goal. Req'd Absolute calibration (K) (110°K-320°K) Inter-channel calibration (K) M118.7± %0.5 K 0.7 K±1 K0.5 K M223.8± %0.5 K 0.7 K±1 K0.5 K M336.5± %0.5 K 0.7 K±1 K0.5 K M489± 1350± 1501K 1,1 K±1 K0.5 K M5157± 1350± 1502K 2.6 K±1 K0.5 K Channel no.FrequenciesPolarisationSpatial resolution (km) M118.7 GHzH+V40 ± 10% M223.8 GHzV40 ± 10% M336.5 GHzH + V40 ± 10% M489 GHzH + V10 ± 10% M5157 GHzH + V6 ± 10%

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October GHz channel of AMSU-B

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October GHz channel of AMSU-B

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October ± 7 GHz channel of AMSU-B

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Monitoring of the Earth Radiation Budget : ScaraB/Megha-Tropiques could partially fill a gap in RB measurements from CERES (Wielicki) Global Precipitation Mission : Madras/Megha-Tropiques to be associated to this multi-satellite mission to increase its tropical sampling. Complementarity to other missions MT

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October )Actions devoted to algorithm developments -Synthetic and Satellite data bases for testing algorithms and processing procedures of the Megha-Tropiques instrumental package. -Microwave rain algorithm developments : adaptation and evaluation of TRMM-based algorithms; specific effort on the ice phase. - Combined geostationary - microwave algorithms. - Radiative fluxes retrievals at different space-time scales. -Humidity retrievals in the perspective of SAPHIR Present scientific developments around MT

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October )Actions devoted to validation of satellite products -Precipitation retrieval validation (raingauges and radars) : sampling and scaling effects. - Validation for other quantities (ice microphysics, others…) -Different methods for water vapour determination (IR and MW sounders, GPS, … ) -General use of the AMMA campaigns and data bases for satellite validation studies - Promoting specific campaigns for water vapour, clouds and radiative budget Present scientific developments around MT

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October ) Actions devoted to MT sampling effects -Use of geostationary observations to simulate the MT sampling of convective systems and their life cycle. To be performed over Africa, India and Brazil. -Development of a simulator for MT from analyses / satellite observations to analyze the impact of MT orbit on the various fields retrieved (radiative budget, water vapour …) Present scientific developments around MT

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October ) Actions devoted to MT thematic science objectives -Many actions in the frame of other tropical research programmes (e.g. AMMA, …) -Opening of a « science team » to the international community expected in depending on CNES-ISRO agreements. Present scientific developments around MT

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Limitations of MT for precipitation determination Megha-Tropiques was not designed specifically for precipitation measurements The space resolution at lowest frequencies of Madras is not sufficient for the size of many convective systems The time sampling is better than for any other microwave instrument, and will be still better when associated to other satellites, but is not sufficient for regions where rainfall occurs in few intensive events. Sampling of the diurnal cycle is very specific with this orbit, and time cumulations have to be adapted to that sampling « calibration » through coincident passes with a space radar -as the mother satellite of GPM- will be very occasional.

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Proposal for a new mission devoted to tropical rainfall TRMM Precipitation Radar is presently the best instrument to measure precipitation from space. It has been proven that its poor time sampling due to the narrow swath can be partially compensated by its association with a proper microwave radiometer. Association with geostationary IR data at 15 minutes intervals is leading to significative improvements in precipitation accumulation estimates (see further presentation on African rainfall during AMMA) The next generation of precipitation radar for GPM will not be in tropical orbit, and its sampling of the tropical area will be poorer than the TRMM PR Precipitation issues in the tropics, in the context of climate change, are vital for the people and countries of this area.

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Proposal for a new mission devoted to tropical rainfall It is proposed to study a new tropical mission (Monsoon Precipitation Mission or MPM) carrying a radar and a radiometer. This mission would be a component of the « virtual constellation » proposed in the context of the CEOS virtual precipitation mission concept, as an extension of GPM The European company « Alcatel Alenia Space » has already performed preliminary studies of the concept of a new space radar. A radiometer has also to be defined. International cooperation with concerned tropical countries will be necessary to go further in the studies of this mission.

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October –Proposed scanning geometry for radar antenna and radiometer antenna Radar across-track scanning –± 17° off-Nadir angle (drives the antenna design & rain cell contamination by ground echo at swath edges) –Around 250 km swath width Radiometer conical scanning –52.8° incidence angle (typical for radiometer) –around1000 km swath width Satellite track Radiometer swath: 800 to 1000 km Radar swath 250 km Range resolution 250 m Footprint <5 km Observed altitude range: ~20 km All rights reserved © 2005, Alcatel Alenia Space Monsoon Precipitation Mission

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Recommended instrument parameters –Orbit altitude : as low as possible Recommended lower than 500 km to decrease antenna size and HPA peak power demand –Around 400 km selected –Footprint : < 5 km Drives the antenna size –Scanning Either Mechanical scanning –Either across-track or conical or Electronic scanning –Only across-track Monsoon Precipitation Mission

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October Comparison with other rain radar instruments Monsoon Precipitation Mission All rights reserved © 2005, Alcatel Alenia Space

IPWG, M. Desbois, Megha-Tropiques, Melbourne, October –Joint consolidation phase to be done to refine Mission specifications with support of scientists Interfaces specification between instrument/platform/launcher Selection of an instrument concept Instrument design and performances Subsystem specifications Instrument mass/consumption/volume budgets assessment Monsoon Precipitation Mission