SMILES sensor

High-sensitivity sensor based on superconducting technology

SMILES receiver uses highly-sensitive superconducting SIS (Superconductor-Insulator-Superconductor) mixers. The superconducting mixers need to be cooled down to a temperature of around 4 K (4 Kelvin, -269 degree Celsius). SMILES employs the mechanical cooler to cool it for the first time in space.

SMILES diagram
Block diagram of SMILES

Signal Flow

Submillimeter-wave radiation from the atmosphere is collected by an offset Cassegrain antenna with an elliptical aperture. These signals are fed to the superconducting mixer (SIS mixer) together with a signal from a local oscillator at 637.32 GHz, and then converted into intermediate frequency signals of 11 to 13 GHz. These intermediate frequency signals are then converted to further lower frequency, and sent to acousto-optical spectrometers (AOS). The observed spectral data and instrumental house keeping data are downlinked to the ground data processing system at Tsukuba Space Center (TKSC) in JAXA via a data transmission system of the ISS.

SMILES Specifications

Observable moleculesO3, HCl, ClO, CH3CN, HOCl, HNO3, O3isotopes
HO2, BrO, SO2, UTH, Ice cloud
Observation frequency Band A624.26 - 625.59 GHz
Band B625.06 - 626.38 GHz
Band C649.05 - 650.38 GHz
Frequency resolution1.05 to 1.20 MHz
SensitivityReceiver noise temperatureTSYS: 297 - 380 K
Precision of brightness temperature ΔT<0.42 K (in 1 ch per 0.5-second integral)
Accuracy of calibrated temperatureΔT< about 1 K
Spatial resolution Antenna diameter392 mm (vertical) × 200 mm (horizontal)
Antenna beam width 0.089° (vertical, full width at half maximum)
Altitude resolutionabout 3.2 km (at the tangent point)
Sampling along the orbit At intervals of about 360 km
Observation altitude range 10 to 60 km (with even higher altitudes being observed by rough sampling)
Observation latitude range 65°N - 38°S
Data rate 44 MB/hour (mission data)
Dimensions 0.8 (wide) × 1 (high) × 1.8 (long) m 0.8 m
Mass476 kg
Power consumption 320 to 500 W
Launch date and end of observationlaunch: 10 September 2009, obs. end: 21 April 2010

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