3. Instrumental Capabilities
3.1 Introduction
3.2 Mission instruments
3.3 Field of view (FOV)
3.4 Spectral regions and sensitivity
3.5 Ground system
3.6 Conclusion

Introduction

ISS and JEM

ISS orbit

Altitude: ~400 km (nominal)
Inclination: 51.6 deg
Period: ~90 min.

SMILES at JEM (KIBO) -EF
Japanese Experiment Module
Exposure Facility

Introduction

SMILES payload
Submillimeter Antenna (ANT)

Submillimeter Receiver (SRX)

IF Amplification Section (IFA)

Radio Spectrometer (AOS)

ANT:
submillimeter antenna
Type:
Offset Cassegrain antenna shaped for
an elliptical beam
Size of main reflector:
400 mm (Vertical) x 200 mm(Horizontal)
Azimuth:Fixed to 45-deg north with respect tothe ISS forward direction
Elevation:
Steerable from –40 deg to +5 deg
Intensity calibration:
With an ambient-temp. load and coldsky

Mission instruments

Mission instruments

ANT performances
Observation Frequency:

624.32 – 650.32 GHz

Main Reflector Aperture Size:

400 (El) x 200 (Az) mm

Main Beam Width:0.09 (El) x 0.18 (Az) degree

Main Beam Efficiency:

Higher than 93 %Return Loss:

Higher than 50 dB

Elevation Angle Range:-40 to +5 degree

Elevation Angle Control Accuracy: +/- 0.01 degree

SRX:
submillimeter receiver

Mission instruments

Type: Cryogenically cooled heterodyne receiver
Submillimeter mixer: SIS mixer with Nb/AlOx/Nb junctions
operating at ~4.3 K
LO source:
Gunn diode oscillator andfrequency multiplierFirst-stage IF amplifier:
HEMT amplifier operating at 20 K
Cryogenics:
Two-stage Stirling cooler plus
Joule-Thomson cooler
Sideband separation:
Modified Martin-Puplettinterferometer (FSP)Mission instruments

SRX performances
Input Frequency:

624.32 – 626.32 GHz (channel-T)
649.12 – 650.32 GHz (channel-R)

Image Rejection Ratio:> 20 dB

LO Frequency:

637.32 GHz

LO Frequency Accuracy:

2 x 10-8

LO Phase Noise:< -87 dBc/Hz (offset 1 MHz)

Output Frequency:

11.00 – 13.00 GHz (channel-T)
11.80 – 13.00 GHz (channel-R)

Gain Non-Linearity:<1%

Gain Variation:< 1 % in 1 minuteReceiver Noise Temperature:

412 – 454 K (channel-T)
345 – 395 K (channel-R)

IFA:
IF amplification section
Type:
Down conversion andamplification
Switching:
Switching to control
signal flow into AOS units
Reference frequency:
Reference CW generation
for AOS frequency
calibration (Comb)

Mission instruments

Mission instruments

IFA performances
Input Frequency:

11.00 – 13.00 GHz (Band-A & B)
11.80 – 13.00 GHz (Band-C)

Output Frequency:

1.55 – 2.75 GHz

LO Frequency Drift:

14 kHz or less

Gain Ripple:

1.2 dBp-p or less in a signal band

Gain Variation:

0.022 dBp-p deg-1 or less

Comb Generator Frequency Step: 100 MHz
Comb Generator Frequency Drift: 5.8 kHz or less

AOS:
radio spectrometer

Mission instruments

Type: Radio spectrometer based on acousto-optical interaction
Light deflector:
LiNbO3-based Bragg’s cell
Laser:
Laser diode emitting at 785 nmDetector:
CCD linear array
Number of Channels:
1728 ch / each CCD
Frequency Resolution:<1.8 MHz (FWHM)

Mission instruments

AOS performances
Input Frequency:

1.55-2.75 GHz

Frequency Resolution:

1.65 MHz or less for channel 1
1.15 MHz or less for channel 2

CCD Number of Channels:

1728 channels / each CCD

CCD Channel Separation:

0.76 – 0.83 MHz

Noise Dynamic Range:
A/D Conversion Accuracy:

9 dB or more(for 10 % additional noise)
12 bits

A/D Differential Nonlinearity:+/-1/2 LSB or less

Data Accumulation:

500 ms

Output Data Length:

16 bits

Output Data Rates:

108 kbps

Mission instruments

SIS mixer
LO: 637.32 GHz
IF: 11-13 GHz
5 mm

LO/RF input:
Corrugated Horn
IF output: SMA

GND

SIS Junction: Nb/AlOx/Nb
Junction Size: ~1 x 1 μm2
Current Density: 6-7 kA/cm2
RF Matching: PCTJSIS Junctions

Waveguide

IF Port50 μm

4 K mechanical cooler

Mission instruments

Two-stage Stirling Cooler (100 K and 20 K)
Joule-Thomson Cooler (4 K)

4K20K100KCooling Capacity:~20 mW @ 4.3K
~200 mW @ 20 K
~1000 mW @ 100K
Mass: 81.6 kg (total)
Cooler
33.2 kg
Cryostat23.9 kgElectronics 81.6 kg
Power Consumption:
265 W @ 125 VDC (BOL)

Running test for >12,000 hr has been
demonstrated (still continuing).

Mission instruments

SRX: image rejection ratio

FSP:
Frequency
SelectivePolarizer

LO SOURCE
ABSORBER

TO COLD SKY
L1 U2

TO ANTENNA
U1 L2ABSORBER

U1 + L1
SIS MIXER 1
ABSORBER

U2 + L2
SIS MIXER 2
CRYOSTATANT+SRX:
beam measurement

Mission instruments

Far-field radiation pattern was estimated fromthe near-field measurement by the phaseretrieval method.
Example of far-field pattern estimated by phase retrieval of phaseless near-fieldmeasurement (637.32 GHz)

Overall performance:

Mission instruments

1. System noise temperature

Band-A

Band-B

Overall system noise temperatureof SMILES measured in the final
performance test.
~500 K for band-A and B, ~450 K
for band-C will be realized in orbit.

Band-COverall performance:

2. Gas cell measurement

Line center [MHz]

H35Cl

H37Cl

Fit result

Catalogue model

625901.65

625901.60(10)625918.71

625918.76(10)625932.04

625932.01(10)624964.33

624964.37(10)624977.77

624977.82(10)624988.28

624988.33(10)Mission instruments

Altitude scanning of the antenna
A single spectral profile isacquired every 0.5 s, in which
the antenna moves 0.056 deg.
Antenna scan period is 53 s:
Limb observation
System gain and the AOS
frequency calibration

Limb path
SMILES

Atmospheric layers

EarthField of view

Global coverage

Field of view

Trajectory for 24 Hours

Covered Latitudes:
65N – 38S (ISS Yaw: 0 deg)68N – 35S (ISS Yaw: -15 deg)
61N – 42S (ISS Yaw: +15 deg)Some information predicts Yaw ~ -4.4 degaround 2009 (~ 66N – 37S?)
Horizontal Sampling Interval:~360 km in orbital direction

The Arctic Region

ISS orbit and attitude variations

Field of view

The ISS is operated according to a number of specific “modes”.
SMILES observation may be discontinued in some modes.
A periodic reboosting of the ISS will be carried out (approximately
every 10 to 45 days?). In the “reboost mode”, drastic variations ofaltitude and attitude due to maneuvering will be expected.

Field of view

Tangent height calibration

Residual errors in the tangent height after calibration with theSTT dataError Factors
Attitudinal Errors:

Sub-mm beam offset from the REF axis
Mechanical driving errors of REF
Thermal bending of REF against STT
Mechanical alignment of REF against STT
STT measurement errors
Time synchronization errors

Altitudinal Error:

Determination errors of the ISS position

Overall (rss):

With the beam offset
Without the beam offset

Bias Error (1σ)

Random error(1σ)

0.13 deg
0.007 deg
0.003 deg
0.007 deg
0.007 deg
0.20 sec

5.02 km0.27 km0.12 km0.27 km0.27 km0.50 km0.007 deg
0.0015 deg
0.07sec

0.27 km0.06 km0.18 km-

0.3 km

-0.1 km5.07 km
0.76 km0.34 km0.34 kmObservation frequency bands
Band-A

Spectral regions

Band-B

Band-CFrequency coverage:
Band-A: 624.32-625.52 GHz
Band-B: 624.32-625.52 GHz
Band-C: 649.12-650.32 GHz
Two of three bands aremeasurable simultaneously.

Sensitivity

Spectral regions“Radio”; radiometric noise, “GFlct”; gain fluctuation, “SW”; standing waves, “DNL”;
differential non-linearity of the analog-to-digital converter, “OA”; overall sensitivity
obtained by rss (root-sum-squares). “unit” means the unit data obtained in 53 seconds.
Standing waves are not reduced by averaging.

Brightness temperature calibration

Spectral regions“KnowError”; knowledge error, “GTV”; time variation of the system gain, “GNL”; nonlinearity of the system gain, “SW”; standing waves, “DNL”; differential non-linearity of
the analog-to-digital converter of the AOS, “Radio”; radiometer noise, and “OA”;
overall error.

Block diagram of ground system

Ground system

EOS: Experiment Operations System

SMILES
In orbit

DPS: Data Processing System

Ground system

Data processing system (DPS)JEM
ICSSMILESNASA

USOS

Operation Control SystemISS

EOS (FOV disturbance check, etc.)

Raw

L0

L1A

DPS-L0/L1

L1B

L2

L3DPS

Ground system

Experiment operations system (EOS)Interface testing with JEM-EF and payloads in Dec. 2007.
Telemetry communication between EOS and SMILES
payload through JEM-EF was successfully demonstrated.

SMILES and JEM-EF (at space station testbuilding)

EOS (right, at space station operationfacility)

Summary of observation capabilities
Frequency Coverage

Band-A:
Band-B:
Band-C:Frequency Resolution:

Conclusion

624.32-625.52 GHz
625.12-626.32 GHz
649.12-650.32 GHz
1.8 MHz (FWHM)

Spatial Coverage
Tangent-point Height:-10 km to 60 km (minimum),(2.1 – 2.4 km sampling)
Latitude:
65 N to 38 S (nominal),(~360 km sampling along the orbit)
Accuracy of Height Determination (after beam-offset cal.)Bias Error:~0.76 km (rms)
Random Error:~0.34 km (rms)Atmospheric Brightness Temperature
Sensitivity (for every 0.5 s):~0.7 K (rms) for Tb < 20 K
~1.0 K (rms) for Tb = 200 K
Accuracy (for every 0.5 s):~1 K (rms) for Tb < 20 K
~3 % (rms) for Tb > 20 K