THE MICROWAVE RADIOMETER PAYLOAD

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Sorrento, Italy Presentation by Marco Cicchinelli (University of L Aquila) M.Montopoli, P.

1 University of L Aquila and University La Sapienza of Rome THE MICROWAVE RADIOMETER PAYLOAD 9th ILEWG International Conference on Exploration and Utilisation of the Moon (ICEUM9/ILC007) -6 October, 007, Sorrento, Italy Presentation by Marco Cicchinelli (University of L Aquila) M.Montopoli, P.Tognolatti (University of L Aquila) F.S.Marzano, M.Pierdicca (University La Sapienza of Rome) G.Perrotta (IMT S.r.l., Rome)

2 A Microwave Radiometric Sounder (MiWaRS), proposed by a mixed team of University of L Aquila and University La Sapienza of Rome, has been selected as a possible choice for flying on board of the ESMO satellite. EUROPEAN STUDENT MOON ORBITER MISSION In March 006, the Education Department of the European Space Agency approved the European Student Moon Orbiter (ESMO) mission proposed by the Student Space Exploration & Technology Initiative (SSETI) association for a Phase A Feasibility Study. ESA (European Space Agency) SSETI association Sponsorship UE University

3 WHY A MICROWAVE RADIOMETER ON THE MOON? Radiometers are highly sensitive receivers designed to measure electromagnetic emission by material media. Microwave have the ability to see things in the dark and then can operate in all lightness conditions. SCIENTIFIC OBJECTIVES OF THE MICROWAVE RADIOMETER: ) Global mapping of the surface and sub-surface surface temperature. ) Global mapping of the lunar microwave emissivity. 3) Estimate of the lunar soil thickness and its properties. 4) Estimate of the lunar sub-surface surface thermal conductivity. There is the need to operate at least at two frequencies: e.g. 3 & 0 GHz in order to accomplish the objectives 3 and 4 3

4 GENERAL SCHEME Definition of an accurate simulation model of surface and sub-surface of the moon. Information about moon stratigraphy. 4

5 LUNAR MODEL 5 ( ) Γ + Γ + ΓΓ Γ = 3 ), ( T L a T L L L p T B θ Moon stratigraphy

6 PRELIMINARY RESULTS λ = 0. m; f = 3 GHz λ = m; f = 4 GHz λ = m; f = 8 GHz λ = 0.05 m; f = GHz T 3 =00 K, ε =4+0.05i, pol=h T = 300 K Brightness Temperature (K) T = 50 K T = 00 K T = 50 K T = 00 K Thickness Layer (m) 6

7 MICROWAVE RADIOMETER SYSTEM For each sensed frequency (or so called: radiometric channels) three hardware elements have to be specified, that is:. Antenna;. Receiver configuration; 3. Reference loads for the calibration unit; 7

MiWaRS ANTENNAS CCH @ 0 Ghz MiWaRS SBF @ 3

9 8.44 4.6 36.4 6.8 θ 3dB H-cut (deg) 64.9 87.

~ 0.47 ~ 0.46 7.99 0,00 Length (cm).5 5..7 9.

8 MiWaRS ANTENNAS 0 Ghz MiWaRS 3 Ghz ө 3dB H~00 km D x Moon surface CCH CCH SBF SBF L θ 3dB E-Cut (deg), x (km) θ 3dB H-cut (deg) x (km) ~ 0.45 ~ 0.48 Main Lobe eff. ~ 0.47 ~ ,00 Length (cm) Diameter (cm) Weight (g) ~ 80 ~ Frequency (Ghz) 3 3 8

9 TITOLO OPEN PROBLEMS In order to perform a good comparison between the information derived from the two radiometric channels, the same IFOV for the two antennas is desiderable. However any improvement of the antenna performances has to observe a tradeoff with size constrains imposed by the available space at the ESMO satellite side. ESMO V (km/s) H=00 Km IFOV LUNAR SURFACE IFOV GHz (Short Back Fire Antenna) IFOV GHz (Corrugated Conical Horn Antenna) POSSIBLE SOLUTION INCREASE OF THE SPATIAL BACKUS-GILBERT RESOLUTION OF THE 3 GHz CHANNEL THEORY 9

10 BASIC RADIOMETER HARDWARE ELEMENTS 3 5 ANTENNA SWITCH RF AMPLIFIER MIXER IF AMPLIFIER 3 DETECTOR DSP 4 DEMODULATION 5 AND INTEGRATION REFERENCE LOADS LOCAL OSCILLATOR 4 0

11 BASIC RADIOMETER HARDWARE ELEMENTS ANTENNA SWITCH RF AMPLIFIER MIXER IF AMPLIFIER DETECTOR DSP DEMODULATION AND INTEGRATION HOT REFERENCE LOAD COLD REFERENCE LOAD LOCAL OSCILLATOR Switches PIN diodes switch SPDT for one reference load, two SPDT or SP3T for two reference loads, with high isolation. Insertion loss < db (for a typical SPDT) and < 3 db (for a typical SP3T) Hot Reference Loads Cold Reference Loads Solid state noise sources with precision high-level noise generation. ENR = 5 db T HOT = 0000 K Active noise sources using colfet. T COLD < 00 K

12 TWO-LOAD AUTO-CALIBRATED RADIOMETER (TLR) It is based on the Total-power configuration; Calibration is implemented during the measure process; HOT REFERENCE LOAD COLD REFERENCE LOAD Goodberlet M. A. et. al., IEEE TGRS, Jan., 006. In a Total-power radiometer the total integration time (τ T ) is entirely dedicated on the observation of the scene; on the contrary In a TLR configuration the total integration time is shared by the scene and the two reference load (generally, it is shared in equal portion);

13 TWO-LOAD AUTO-CALIBRATED RADIOMETER () Advantages: We have not problem to define when to make the calibration operation; Radiometric resolutions below K are expected from our preliminary analyses (for total integration time up to s); Drawbacks: Like in other radiometric configurations, we have to consider the possible gain and offset variations of the receiver that can alter the measurement process; Possible solution: Selection of an appropriate integration time, in which the errors connected to the gain and offset variation are less then the ideal radiometric resolution ; 3

14 EFFECTS OF GAIN AND OFFSET VARIATIONS Introducing the chopping half-period τ C Generally we have: τ = C τ T Tg vs τ C Gs(τ)/Gs=0-5 (/s) Gs(τ)/Gs=0-6 (/s) Gs(τ)/Gs=0-7 (/s) IDEAL Ta 0.5 To vs τ C Os(τ)= (mk/s) Os(τ)=5 (mk/s) Os(τ)=0 (mk/s) Os(τ)=50 (mk/s) IDEAL Ta Tg [K] 0.05 To [K] chopping half-period τ C [s] chopping half-period τ C [s] 4

15 Features of the MiWaRS Antennas Type: SBF & CCH Freq.(GHz) 3 & 0 Weight (g): θ 3dB E-cut (deg) CFET Ther. Ref Hot ref (K) Cold ref (K) Hot ref. Power (W) >350 <00 θ 3dB H-cut (deg) Hot ref. weight (g) 88 Receiver ML eff Gain (db): Cold ref. weight (g) 65 NF System B (MHz): 00 Weight LNB (g): *70 Size (cm) 0x0x0 Sensitivity (K) <0. Int. time (sec) 4 Power peak (W) <0 Data rate (Mbit/day).4 General performances Weight (kg) <.5 Without shield Size (cm) 0 x 0 x0 Without antennas Power peak (W) <0 5

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