Mars Express Data Workshop ESAC, Villafranca del Castillo Madrid (Spain) MARSIS Instrument & Operation Concepts 9 -11 June 2008 Andrea Cicchetti Raffaella Noschese, Marco Cartacci, Stefano Giuppi

Table Of Contents MEX Orbital Configuration. MARSIS Working Range. Night Time Environment. Day Side Environment. Example of MARSIS Timeline. Main Instrument Parameters. MARSIS Block Diagrams . Tracking and Acquisition Concepts. Doppler Processing. Raw Data Collection (Flash Memory Utility) Global Coverage per Band achieved until 29/Feb/08 Phobos Observation Criteria and latest Results. Overview of the Support Tools

1 MEX Orbital Configuration Periapsis ~ 300Km Apoapsis ~ 10.000Km N w ORBIT 5851 Event UTC PERI 2008 JUL 23 03:37:24 MEX Orbital Plane Mars Mars Express was successfully launched on 2 June 2003 from Baikonur, Kazakhstan, by a Russian Soyuz rocket. Following a cruise of almost 7 months, the SC was captured into orbit on 25 December 2003 and soon established a highly elliptical polar orbit with a closest approach to the surface of about 300 Km and a period of about 6.65 h MARSIS Working Slot

Sub Surface Sounding Modes or AIS 2 MARSIS Working Range ~ 300Km SC Altitude Mars ~ 1200Km ~ 900Km AIS 5 min Sub Surface Sounding Modes or AIS 30 min MARS Pericenter

3. Night time Environment H2O Deposit ~ 5 Km MARS Surface MARS Sub Surface ~130 Km Soft Ionosphere Layer 1.8 MHz 3.0 MHz Good Penetration Capabilities  Dipole antenna Monopole antenna

Acceptable Penetration 4. Day time Environment H2O Deposit ~ 1-2 Km MARS Surface MARS Sub Surface 4.0 MHz 5.0 MHz Dipole antenna Monopole antenna 80 ~130 Km Strong Ionosphere Layer Acceptable Penetration Capabilities  The lowest Bands (1.8 and 3.0 MHz) Will be completely reflected by the Ionosphere layer

Upper Ionosphere Layer in the day side 4.1 Ionosphere Reflection proprieties in the day side In the deep day side it is not possible to use the lowest radar bands due to the upper ionosphere layer that will completely reflects the MARSIS Signals. Band 1 (1.8 MHz) Mars Surface Orbit 4628 (11/Aug/07) 295.7 Km 150 Km Upper Ionosphere Layer in the day side 145.7 Km

5 Example of MARSIS Timeline SC [SEA]/Altitude AIS Time Off Peri [min] -15° SS3 B1/B2 B2/B3 B3/B4 0° 35° -20.0 -15.0 0.0 15.0 20.0 ~1200 Km ~ 900 Km ~900 Km ~ 300 Km Day Side

6 Main instrument Parameters Sub Surface Sounding Parameters Centre Frequencies: Band 1  1.8 MHz Band 2  3.0 MHz Band 3  4.0 MHz Band 4  5.0 MHz Bandwidth = 1.0 MHz δ= 150m (free space depth resolution) Transmit pulse Length = 250 us PRF = 127.267 Hz (Pulse Repetition Frequency) Receive Window Size = 350us Sounder Dynamic Range = 40 to 50 dB Surface Sounding Altitude Range = 250 to 900 Km Ionospheric Sounding Parameters Maximum Altitude = 1200 Km Frequency Range = 0.1 to 5.5 MHz δ= 15 Km Bandwidth = 10 KHz Transmit Pulse Length = 91.43 us Minimum Frequency Step = 10.937 Hz Repetition Period = 7.38s Dipole Antenna element length = 20 m Monopole Antenna length = 7 m Total Mass = 20 Kg DC Operation Power = 60 W

7 MARSIS Block Diagram S/C 1 4 3 2 MARSIS Consist of : Power And Control Processor S/C Transmitter Receiver Signal Generator Analog to Digital Converter 1 2 3 4 Monopole Dipole I/Q Synthesis MARSIS Consist of : A sounder channel containing a programmable signal generator a surface cancellation channel a dual channel data processor a power and control subsystem which controls all the sounder functions A/D Converters  Operate at a Sampling frequency of 2.8 MHz (8 bit)

7.1 Subsurface Sounding Processing Functionalities Ionospheric Calibration Tracking Acquisition Passive Sounding Range & Doppler Processing Data Presumming Timing System From I/Q Synthesis

7.2 Subsurface Sounding Mode SS1 (2 Frequencies – 2 Antennas – 1 Doppler Filter) Tx Phase TX 1 2 250 us 450 us t [us] Two frequencies operation: four echoes are received, two from Dipole channel and two from Monopole channel. Echoes are processed to synthesize a single Doppler filter. Complex data for each of the four synthesized Doppler filters, before range compression, are transferred in the science source packet data format. This mode allows coherent clutter cancellation on two frequency bands by means of dual antenna clutter cancellation ground processing. Rx Dipole Ch RX 1 2 450 us t [us] Trigger Rx Monopole Ch RX 1 2 450 us t [us] Trigger

No signals processed from Monopole 7.3 Subsurface Sounding Mode SS2 (2 Frequencies- 1 Antenna (dipole) – Onboard Multi-look) Tx Phase TX 1 2 250 us 450 us t [us] Two frequencies operation: two echoes are received, two from Dipole channel. Echoes from the Monopole channel are not processed, while echoes from the Dipole channel are processed to provide a Multilooked information for a single Doppler filter using parallel synthesis of five Doppler filters on board. The power detected samples for each of the two multilooked Doppler filters synthesized are transferred in the science source packet data format. Rx Dipole Ch RX 1 2 450 us t [us] Trigger Rx Monopole Ch t [us] No signals processed from Monopole Channel

99.99 % Of the data have been collected with this modality 7.4 Subsurface Sounding Mode SS3 Tx Phase TX 1 2 250 us 450 us t [us] Two frequencies operation: This mode allows downlink, for each frame, of the I and Q data of three Doppler filters collected on the dipole antenna channel at two frequencies. Range processing is performed on the ground. Rx Dipole Ch RX 1 2 450 us t [us] Trigger 99.99 % Of the data have been collected with this modality Rx Monopole Ch t [us] No signals processed from Monopole Channel

7.5 Subsurface Sounding Mode SS5 Tx Phase TX 1 30 us t [us] 2 3 4 Single frequency operation: two echoes are received, one from the Dipole and one from the Monopole. Echoes are actually pre-summed over groups of four to increase the Signal to Noise Ratio. Pre-summed Echoes are processed to synthesize three central Doppler filters for each channel. Complex data of the six synthesized Doppler filters before range compression, are transferred in the science source packet data format. This mode uses a short pulse waveform to reduce the impact of uncontrolled sidelobes on deep subsurface reflections Rx Dipole Ch t [us] Trigger TX 1 2 3 4 Rx Monopole Ch t [us] Trigger TX 1 2 3 4

“ Calculated by MARSIS” 8 Tracking & Acquisition Concepts Mars Transmitter Acquisition Modality Range Compression & Ionosphere Compensation Azimuth Compression Receiver A/D Buffer Preset Trk H = 674Km Set by the User Trig ~ 4493 us “ Calculated by MARSIS” AGC Tracking Range Tracking LoL Logic Tracking Lost Preset Trk ? yes not

8.1 Timing of Tracking and Acquisition NPN Rx Gate Acq. 1400 us 365.71 us 91.43 us 1000 us Rx_Trig_Acq Passive Ionosphere Gate ACQ Band = 200 KHz Acquisition Timing Tx F1 350 us 91.43 us 250 us Rx_Dist_F1 Passive Ionosphere Gate TRK Band = 1.0 MHz Tracking Timing (SS3) Tx F2 Rx Gate F1 Rx Gate F2 450 us Rx_Dist_F2

8.2 Tracking Initialization Overview (Worse Case) MARSIS starts to operate Ionosphere Layer  100 us is the maximum delay in the day H = 400 Km 2666.7 us Rx Phase Time [us] 250 us 400 Km  2666.7 us Extra delay 350 us 150 us Chirp Length 50 us Lost MEX Orbit h~7.5 Km 50us Hellas Planitia (minimum depression) Mars Topography Range Polynomial Coefficients

8.3 (Timeline) Example of the Tracking effect SS3 B3/B2 OST 4 SC [SEA]/Altitude AIS OST 7 Time Off Peri [min] B4/B3 OST 3 OST 0 12° -18.0 -13.0 -7.5 -1.5 13.0 18.0 761 Km B2/B1 OST 5 5° 478 Km -5° 314 Km 763 Km -23° Orbit 1885 – 4/July-2005 “ First Routine Orbit” Fake SS2 “Tx Slow Power UP” -No Science- Fake SS3 (15”/30”) “Band inversion Before each AIS” B1/B2

8.4 (Level 2 data) Example of the Tracking effect OST 3 (B4) OST 4 (B3) OST 5 (B2) Trigger Offset Trigger Compensated “L2 Product from PSA” Tracking Lost “Low SNR”

8.5 (Level 2 data) Example of the Tracking effect Tracking lost due to the low SNR rate.

9 Doppler Processing 9.1 Observation Geometry Range Range MEX DPL Range Along Track Where: H  SC altitude δ  Range Resolution (150m) MEX Fly direction δ H Range Along Track Cross Track DPL MEX Fly direction Main Contribution From the Mars Surface Dipole Antenna Monopole Antenna

On Board Doppler Processing Range Along Track Cross Track DPL MEX Fly direction Main Contribution From the Mars Surface Dipole Antenna Monopole Antenna Data Acquisition Range Along Track Cross Track DPL MEX Fly direction Main Contribution From the Mars Surface Dipole Antenna Monopole Antenna Increased Azimuth Resolution On Board Doppler Processing

10. Raw Data Collection (Flash Memory Utility) SS3 B3/B2 B4/B3 SEA=0° -120 S 0.0 S -300 S Raw Data Start Acq. Orbit 3990 Start Lat=12.4N P-60 (Time Off Pericenter) Science Area Of Interest On Board Processing Raw Data Collection Flash Memory SC Interface Dipole Antenna Flash Memory Blocks Diagram

11. Global Coverage achieved until 29/Feb/08 MARSIS Operation Centre Main Archive All Frames SNR Evaluation SW Global Coverage Sub Archive Optimum Frames Generic Fr … Generic OST Line Ch1 Generic OST Line Ch2 18 dB Frame Selection within an OST line Generic Frame, SNR ~ 18 dB

11.1 Band 2 Global Coverage

11.2 Band 2 Global Coverage

11.3 Band 3 Global Coverage

11.4 Band 4 Global Coverage

Minimum Flyby distance: 12. Phobos Observation Criteria and latest Results MEX Orbital Plane Closest Approach “ Phobos Data Take” Mars Phobos Periapsis ~ 300Km Apoapsis ~ 10.000Km Encounter Approach Departure Orbit number: 5851 Time Period 2008 JUL 23 04:50:51 Minimum Flyby distance: 93 km !!

12.1 Limitation of the Standard Onboard Configuration Protection Zone Range [Km] Offset Time [us] 1600 -1600 240 ~ 93 Working Zone With the standard on board configuration it is not possible the Phobos detection

12.2 Timing of the Standard on board configuration Tx Phase TX 1 2 250 us 450 us 700 us Time [us] RX 1 2 RX1 RX2 50us of margin (7.5 Km) Rx Phase Time [us] SW limitation 1600 us 1600+50 us us 240+7.5 Km

12.3 Techniques to reduce the instrument Protection Zone 12.3.1 Reduction of the SW limitation “First level of range extension” Tx Phase TX 1 2 250 us 450 us 700 us Time [us] 247.5Km  240Km. 7.5Km less !! SW limitation Rx Phase RX 1 2 RX1 RX2 240 Km Time [us] 1550 us 1600 us

12.3.2 Ambiguity Technique “Second Level of Range Extension” Tx Phase 250 us 250 us TX 1 TX 2 Time [us] 450 us 700 us 450 us 67.5 Km Rx Phase SW limitation RX1 RX2 RX 1 2 Time [us] 1550 us

12.3.2.1 Timing of the ambiguity Technique Tx Phase 250 us 250 us 240Km  157.5Km. 82.5 Km less !! TX 1 TX 2 Time [us] 450 us 700 us SW limitation 1550 us Rx Phase RX 1 2 RX1 RX2 450 us 1150 us 157.5 Km Time [us]

12.3.3 Margin back in the game (50+125us) “ Third level of range extension” Tx Phase 250 us 250 us 157.5Km  146.25Km. 7.5Km+3.75Km=11.25 Km less !! TX 1 TX 2 Time [us] 450 us 700 us 247.5Km  146.25Km. 101.25 Km less !! SW limitation 1550 us Rx Phase RX1 RX2 975 us 146.25 Km RX 1 2 450 us 125 us

12.4 Overview of the Reduced Protection Zone Range [Km] Offset Time [us] 1600 -1600 240 ~ 93 Working Zone 975 -975 146

12.5 Consolidated Timeline and prediction of the results CAL Low Power TX Slow Power Up PREO STBY Medi POST SS3 B3/B3 36” AIS 2m0” 1m57” -75 -39 39 75 195 315 -177 -279 -399 -699 235 Km 146 Km ~ 93 Range [Km] Offset Time [us] Total Number Frames = 36+36 = 72 Total Number of echoes = 3240 + 3240 = 6480

12.6 Latest Phobos flyby results 07/Oct/2007 Display of the generic echo MEX Fly direction SNR÷20dB

Overview of the Matlab Support Tools

13 Overview Of the Support Tools 13.1 Support Tool “Basic Level” Get File Read Header fields Read Scientific Data Linear/dB Conversion Write Outputs Files Display Plots FRM_SS3_TRK_CMP_RDR_1885.DAT Output Files

13.1.1 Basic Level Tool “Main Output” Generic Frame Science Data Header Data 1 94 95 607 94 Elements 512 Elements

13.2 Support Tool “Advanced Level” Get File Read Header fields Read Scientific Data FRM_SS3_TRK_CMP_RDR_1885.DAT LineardB Noise Evaluation dB Linear Multi Look Write Outputs Files Display Plots Output Files

13.2.1 Advanced Level Tool “Noise Attenuation Concepts” 350us t [us] Pwr [dB] Noise Estimation Slot 350us t [us] Pwr [dB] Noise Level 350us t [us] Pwr [dB] Noise Level Noise Attenuation Pwr [dB] 350us t [us] 350us t [us] Pwr [dB] Noise Estimation Slot Shift back of the peak

13.2.2 Advanced Level Tool “Main Output” Multi Look Representation The filters (-1,0,+1) collapse in one Radargram (multi look)

13.2.3 Advanced Level Tool “ Radargram without the Noise attenuation, Noise_Att=1”

13.2.4 Advanced Level Tool “ Radargram with Noise attenuation, Noise_Att=0.8”

13.2.5 Advanced Level Tool “Single frame visualization, without noise attenuation”

13.2.6 Advanced Level Tool “Single frame visualization, with noise attenuation”

13.2.7 Advanced Level Tool “ Radargram without any range offset”

13.2.8 Advanced Level Tool “ Radargram shifted of 100us down”