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SMILES Mission: Submillimeter Sensor Technology for Global Atmospheric Observations

Experience the innovative SMILES (Superconducting Submillimeter-Wave Limb-Emission Sounder) mission, offering high sensitivity and fine spectroscopy to study trace gases and global dynamics in the atmosphere. Utilizing cutting-edge technologies like superconductive mixers and mechanical coolers, SMILES aims to provide unique insights into the Earth's atmospheric processes and chemical composition. Join us in unraveling the mysteries of ozone depletion and understanding atmospheric mechanisms with real-time global observations.

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SMILES Mission: Submillimeter Sensor Technology for Global Atmospheric Observations

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  1. Introduction to SMILES Mission Objectives Space Demonstration of Submillimeter Sensor Technology based on a Superconduvtive Mixer and 4-K Mechanical Cooler Experiments of Submillimeter Limb-Emission Sounding of the Atmosphere Global Observations of Trace Gases in the Stratosphere and Contribution to the Atmospheric Sciences

  2. Scientific Objectives Understanding global mechanism of ozone depletion • Overall chemical processes: => Multi-species observations • Global dynamics & Regional interactions: => Global 3-D observations Advantages of SMILES • High sensitivity: => Real-time map without spatial averaging • Fine spectroscopy: => High detectability for minor weak species

  3. Limb Sounding from ISS

  4. Molecular Emissions: LSB Band-1:624.32 - 625.52 GHz Band-2:625.12 - 626.32 GHz Band-1: O3, H37Cl, HNO3, BrO Band-2: O3, H35Cl, HO2

  5. Molecular Emissions: USB Band-3:649.12 - 650.32 GHz Band-3: ClO, HO2, O3, BrO, O3-isotopes

  6. Global Mapping Latitudes Coverage: 65 N to 38 S Trajectory of Tangent Points in 24 Hours Distribution of atmospheric regions sampled in consecutive frames of antenna scanning. Length of each frame is 53 sec.

  7. Signal Flow in SMILES Submm Signal is down-converted: => 11 - 13 GHz => 1.55 - 2.75 GHz Emission-line Spectra are derived by AOS (Acousto-optic Spectrometer).

  8. View of SMILES Alignment Panel ADE EPS SJTD AOPT AOS CST Cryostat STT DPC ANT

  9. Submillimeter Receiver Key Technology Superconductivity Electronics (SIS mixer) Cryogenic LNA Technology (HEMT amplifiers) Submillimeter Devices & Components Submillimeter Quasi-optics Cryostat Technology (4K level) Mechanical Cryo-cooler Technology (4k level)

  10. Receiver Sensitivity: SIS vs SBD SBD mixer receiver SIS mixer receiver hf/k: Quantum Limit Superconductive SIS mixer receivers have some 20 times higher sensitivity than conventional Schottky-diode mixer receivers for frequencies less than 700 GHz.

  11. 640 GHz SIS Mixer Nb/AlOx/Nb Device 1.2 um x 1.2 um, 5.5 kA/cm2 Fabricated at Nobeyama Radio Observatory

  12. Cooled HEMT Amplifiers 20K-stage Amplifier 100K-stageAmplifier Tphys = 300K Vd = 2V, Id = 10mA Tphys = 300K Vd = 2V, Id = 10mA Tphys = 100K Vd = 1V, Id = 5mA Tphys = 20K Vd = 1V, Id = 5mA Two HEMT Devices: FHX76LP Gain: 20-22 dB @300K 23-26 dB @20K Three HEMT Devices: FHX76LP Gain: 28-32 dB @300K 30-33 dB @100K Nitsuki Ltd.

  13. Submillimeter LO Source BBM by RPG/Ominisys Gunn Phase Noise: < -90 dBc/Hz @ 1MHz Submm Freq. Stability: 1 x 10^(-8) /deg

  14. Receiver Optics Ambient -Temperature Optics < Two Functions > - RF/LO Coupling - Sideband Separation Cooled Optics

  15. SSB Filter with FSP’s • Single Sideband Filter: To separate USB and LSB signals • Frequency-Selective Polarizer: • Suitable for a fixed-frequency application • Extremely low reflection --- Low standing waves SSB Filter (BBM) by Thomas Keating Ltd.

  16. SRX Subsystem To Antenna Ambient Temperature Optics Cryostat AOPT To Cold-Sky Terminator AAMP Single Sideband Filter Sub-mm LO Source CREC He Compressor (JT) He Compressor (ST)

  17. Thermal Design of SMILES Requirements State-of-the-art cryogenicdesign is needed to keep SIS mixers at 4.5 K, HEMT amplifiers at 20 K /100 K. Ambient-temperature Thermal Design is based on the Use of Coolant (FC-72) Detail Analysis is Needed on Influences of Radiation Coupling to Space High Temperature Stability is Needed for the Stable Operation of the Receiver

  18. Cryogenics • Requirements • SIS Mixers & Cooled Optics @ 4.5 K • HEMT Amplifiers @ 20 K & 100 K • Mechanical Cooler • Cooling Method: Two-Stage Stirling & Joule-Thomson • Cooling Capacity: 1000 mW @ 100 K 210 mW @ 22 K 20 mW @ 4.5 K • Power Consumption: 210 W (Coolers) + 90 W (Loss in PS)

  19. Cryostat Radiation Shield: MLI (40 layers) Signal Input Window: IR Filters (‘Zitex’) Support for 100 K Stage: S2-GFRP Straps (12 pieces) Support for 20 K Stage: GFRP Pipes (4 pieces) Support for 4 K Stage: CFRP Pipes (4 pieces)

  20. Thermal Design of Cryostat Window:Heat flow is reduced with two IR filters IF cables:CuNi coaxial cables HEMT current:Circuit is optimized for a Starved Bias Condition JT load:Minimized by reducing the rate of GHe flow

  21. Two-stage Stirling Cooler

  22. Joule-Thomson Cooler Cryostat (inc. ST Cold Head): 29 kg Stirling Compressor: 10 kg JT Compressors (2 units): 15 kg GHe Piping: 7 kg Control & Drivers: 23 kg

  23. I/F Conditions: IN: 16-24 C, OUT: 16-50 C Flow of Coolant FC-72 Cryo-cooler (STC, CRST, JTC) and AOS need to be cooled at less than 30 C.

  24. Concept of Thermal Control Radiation coupling to space occurs through HCAM, FRGF and Antenna. This effect should be connected with the analysis for the coolant.

  25. SMILES Output Data • H/K and Attitude Data:1553B • Spectroscopic Data: Ethernet • Data Rate: 120 kbps, continuous No Mass Data Storage installed in SMILES. Spectroscopic Data down-link to NASDA/TKSC will be established through JEM/ICS link (via DRTS). ICS: Inter-orbit Communication System DRTS:Data Relay Test Satellite

  26. SMILES on-orbit Data Processing To JEM (PDH, PEHG) Ethernet(10Base-T) 1553B 100 kbps 20 kbps

  27. SMILES Observation Profile • Limb emission spectrum is measured every 500 ms • Limb scan is finished in 53 sec. Main Antenna 6 Altitude coverage between 0 and 60km is guaranteed Hot Load for reference 4 Relative scan angle (degree) 2 0 Cold Sky for reference Switching mirror 30 0 0 10 20 30 40 50 60 Time (s) Antenna scan profile

  28. SMILES Radio Spectrometer • Bandwidth: • 1200 MHz x 2 units • IF: 1.55 - 1.75 GHz / unit • Focal Plane: • 1728-ch. CCD array x 2 units • Frequency Resolution: • 1.8 MHz (FWHM) • cf. Channel Separation: 0.8 MHz / ch. • AD Conversion: • 12-bit, 2-CCD readouts in 4.9 msec • Adder Output: • 16 bits x 1728 ch. x 2 units in 500 msec Acousto-Optic Spectrometer (Astrium & OPM)

  29. Data Processing and Products Raw Data Level_0 Data Level_1 Data Level_2 Data Level_3 Data ~ 120 kbps Bit Stream Overlap Correction, Time Sequence Rearrange Edited Data ~ 1.24 GB/day Radiometric Calibration etc. Engineering Data (Brightness Temp.) ~ 2.5 GB/day Retrieval Height Profiles along Orbit ~ 170 MB/day Averaging and Gridding Global Map

  30. ISS Ground DataProcessing DRTS NASDA/ TKSC Raw Data NASDA/TKSC CRL Level_0 Level_0 Univ. Bremen Level_1 Level_1 Level_1 Level_2 Level_2 Level_2 Level_3B Level_3 NASDA/ EORC Level_2 WWW WWW Anonymous Users Level_3A ftp, WWW ftp, WWW Registered Users

  31. SMILES Level-2 Data Expected Estimated Error Example : Altitude profile of ClO volume-mixing-ratio

  32. Concerns in SMILES Data Down Link • Effective Bandwidth of Ethernet in JEM is limited . • JEM/ICS link is yet to be improved to cover our mission requirements. SMILES Mission Requirements: Nominal data rate 100 kbps Continuous observation No necessity for real time link

  33. ISS Environmental Issues Compatible Design Needed Deterioration of environmental vacuum may occur due to contamination. Measures needed to protect SMILES operation. Space Shuttle: Water Dumps JEM-PM: Cabin Air Vents Some EMI may deteriorate the data quality of SMILES, even if it is too low to damage the instruments. Most careful measures for EMI are indispensable. EM-shielding designs are taken.

  34. External Contamination around JEM-EF JSpace Shuttle Water Dumps Space Shuttle dumps fuel-cell water approximately every three days, with the flow rate of ~64kg/45min. JJEM Vacuum System Vents JEM-PM vents cabin air to provide low-pressure environments for internal payloads, and to depressurize the airlock for EVA. JInternal/External Outgassing J Natural Environment

  35. J Thermal Isolation in the Cryostat Pressure in the cryostat must be kept below ~10-6 Torr for the thermal isolation. → A vacuum valve of the cryostat should be closed during high-pressure periods. Major Impacts on SMILES J Reflection / Transmission Loss of the Optics Water stuck on optical surfaces causes reflection / transmission losses (e.g. ice film with a thickness of ~7mm will result in a transmission loss of 1% at 640 GHz). → Sticking fraction on the optics should be evaluated.

  36. Ventilation from JEM-PM JEM vent locations and directions (left panel), and pressure distribution around JEM-EF during the JEM6A/6B operation (right), calculated by SED (2000).

  37. Water Dump from Shuttle Radial Dispersion Angular Dispersion Dispersion of the water flow calculated by Boeing (1998).

  38. Shield against ISS Environmental Fields

  39. Design Concept • Twofold Electromagnetic Shields: • EM-Shield by System Enclosure: Isolation > 20 dB (Target) • EM-Shield by Receiver Cryostat: Isolation > 60 dB (Target) • To Suppress Radiation Leakage: • Complete Gap Sealing for Enclosure Panels • Indium-coated “O-ring” for All Flanges in the Cryostat • “Back-to-back Horn” for Antenna/Receiver Interface (Cut-off Waveguide against EMI at 27.5 GHz or less) • To Suppress Leakage through Cables: • Use of Shielded Cables • Use of EMI-shielded Connectors • Use of Low Pass Filters • Strict EMI Design in Each Component

  40. Electromagnetic Shielding

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