ADEOS-II (Advanced Earth Observing Satellite-II) / Midori-II

ADEOS-II is a Japanese (JAXA, formerly NASDA) Earth environmental observation satellite, a successor mission to ADEOS with international cooperation. Overall objectives are to provide and improve Earth observation services with advanced payload instruments.

The science objectives of ADEOS-II are to acquire data contributing for international global change research (carbon cycle and the water and energy cycle), as well as for applications in such fields as meteorology and fishery. ADEOS-II is the Japanese contribution in the framework of the International Earth Observation System (IEOS). Other parts of IEOS are EOS (USA), and the ENVISAT and MetOp programs of ESA and EUMETSAT, respectively. The ADEOS-II mission, also referred to as Midori-II, is dedicated to the following programs: WCRP/GEWEX & CLIVAR, IGBP and GCOS. ^{1) 2) 3) 4)}

Figure 1: Illustration of the ADEOS-II spacecraft (image credit: NASDA)

Spacecraft:

The ADEOS-II S/C, built by Mitsubishi Corporation, employs the general design of ADEOS to reduce costs. Dimension of main S/C body: approximately 6 m x 4 m x 4 m. S/C mass = 3700 kg, payload mass = 1300 kg, power = 5.3 kW (EOL), launch vehicle = H-IIA rocket, launch site = TNSC (Tanegashima Space Center). Attitude and Orbit Control: The AOCS (Attitude and Orbit Control Subsystem) employs a three-axis strap down attitude detection system and zero momentum attitude control system achieving an attitude pointing error of < 0.3º. A GPS receiver provides onboard timing and orbit position services. The design life of the spacecraft is three years minimum with a goal of five years (propellant).

The ADEOS-II spacecraft consists of a mission module, equipped with observation instruments, and a bus module where the avionic subsystems are mounted (Table 1).

Table 1: Overview of the S/C avionic subsystems allocated to the bus module

Figure 2: Alternate view of ADEOS-II (image credit: NASDA)

RF communications: Mission data are downlinked in X-band to ground receiving stations. The S-band is used for TT&C support. In addition there is communication link via DRTS (Data Relay and Test Satellite) in Ka-band for mission data and S-band for TT&C data. This communication link is referred to as IOCS (Inter-Orbital Communication Subsystem).

Figure 3: Overall configuration of the ADEOS-II ground system (image credit: NASDA)

Orbit: Sun-synchronous subrecurrent orbit, altitude = 802.9 km, inclination = 98.62º, period = 101 minutes, recurrent period = 4 days, local sun time = 10:30 AM ±15 minutes.

Launch: A launch of ADEOS-II on a H-IIA vehicle took place on Dec. 14, 2002 from TNSC (Tanegashima Space Center), Japan, along with FedSat of Australia, WEOS of the Chiba Institute of Technology (Chiba, Japan), and MicroLabSat of JAXA, NICT and CRL as secondary payloads on the mission.

Mission status: The ADEOS-II mission was operational for only 10 months.

• On Oct. 24, 2003, ADEOS-II experienced a severe power failure, stopping all mission operations. JAXA formed immediately the "Midori-II anomaly investigation team." However, the nature of the failure prevented any recovery that would have led to a continuation of the mission. ⁵⁾

One of the two main working hypotheses into its cause was that a debris impact on the high-power harness carrying current between the single solar array and the satellite bus resulted in a sustained electric arc. The harness consisted of a bundle of wires covered by a sheet of multi-layered insulation (MLI).

• NASDA successfully conducted the intersatellite communication experiment between ADEOS-II and ARTEMIS (Advanced Relay and Technology Mission) of the European Space Agency (ESA) from March 28 to 30, 2003. This experiment used both links for data transmission; the Ka-band (26 GHz) for payload data and the S-band (2 GHz) for TT&C services.

• A successful communication experiment between ADEOS-II and DRTS (Data Relay Test Satellite) took place on Feb. 19, 2003. ⁶⁾

Sensor complement: (AMSR, GLI, ILAS-II, SeaWinds, POLDER-2, Argos Next)

The ADEOS-II payload comprises six instruments: NASDA's AMSR (Advanced Microwave Scanning Radiometer) and GLI Global Imager), NASA/JPL's SeaWinds scatterometer, the Japanese Environment Ministry's ILAS-II (Improved Limb Atmospheric Spectrometer-II), POLDER-2 (Polarization and Directionality of the Earth's Reflectance) of CNES, and the Argos-Next data collection instrument developed jointly by NASDA and CNES. ⁷⁾

AMSR (Advanced Microwave Scanning Radiometer), a passive NASDA core sensor of MSR heritage flown on MOS-1 and MOS-1B satellites. Objectives: measurement of sea surface temperature (SST), soil water content (moisture), sea wind speed, water equivalent of snow cover, precipitation intensity, sea ice distribution, precipitable water, etc. Microwave emission from the atmosphere, ocean, sea ice, and land are measured at multiple frequencies. From this information a number of geophysical data related to the Earth environment, such as water vapor content, water content of clouds, water equivalent of the snow cover, etc. are measured. - A further instrument, AMSR-E, was developed by NASDA, it is flown on NASA's Aqua mission. ^{8) 9)}

AMSR is an eight-frequency, total-power microwave radiometer (a passive sensor) with dual polarization (except two vertical channels in the 50 GHz band). It detects microwave emissions from the Earth's surface and atmosphere. Conical scanning at 40 rpm is employed to observe the Earth's surface with a constant incidence angle of approximately 55º (a scan drive motor rotates the antenna, rotating mass is nearly 200 kg, momentum and torque compensation is achieved with momentum wheels). Multifrequency measurements are realized by arranging multiple feed-horns, and by staggering their integration timing to compensate the differences of beam direction. The 89 GHz band has two feed horns (A/B) to permit enough sampling in the along-track direction. The AMSR 2.0 m diameter offset parabolic antenna is the largest spaceborne microwave radiometer antenna of its kind; it provides reasonable spatial resolution even in lower frequency channels.

AMSR has a high-temperature calibration source (about 340 K) and a small reflector to acquire the radiant temperature of deep space (at about 3 K). This is a so-called "external calibration scheme" was first introduced by SSM/I (Special Sensor Microwave/Imager) on DMSP satellites. Each feed horn, from 6.9-89 GHz sees the calibration sources once per scan period. In addition, extensive pre-launch characterization/calibration activities were done.

Table 2: AMSR parameter definition

Figure 4: Schematic view of AMSR instrument (image credit: NASDA)

Figure 5: Scanning geometry of the AMSR instrument (image credit: NASDA)

GLI (Global Imager), an optical NASDA core sensor of OCTS heritage on ADEOS. Objectives: Biological and physical processes, stratospheric ozone. GLI is for studying and monitoring the carbon cycle in the ocean, principally as to biological processes. Multispectral observations from the near UV to the near IR reflected solar radiation from the Earth's surface including land, ocean and clouds. Determination of chlorophyll pigment, phycobilin and dissolved organic matter (DOM) in the ocean; classification of phytoplankton according to their pigment. Measurement of sea surface temperature (SST), cloud distribution, land coverage, vegetation index, etc. ^{10) 11) 12) 13)}

GLI is a 36-channel VIS/IR radiometer/imaging spectrometer (opto-mechanical instrument) featuring a cross-track mirror and an off-axis parabolic mirror as the collecting optics and focal planes in which the detectors are arrayed in the along-track direction with spectral interference (dichroic) filters. The scan mirror rotates at 16.7 Hz. GLI can tilt the scan mirror ±20º from nadir in order to avoid sun glitter. GLI has five focal planes, two for VNIR, two for SWIR, and one for MWIR/TIR. Two VNIR focal planes have detector arrays for 13 and 10 bands respectively. Two SWIR focal planes have detector arrays for 4 and 2 bands, while the MWIR/TIR regions have one focal plane with a detector array for 7 bands. One SWIR and the MWIR/TIR focal planes are cooled to 220 K and 80 K by a multistage Peltier element and Stirling cycle mechanical cooler, respectively. The VNIR detector material is Si, the SWIR is InGaAs, the MWIR/TIR material is CMT.

GLI employs piecewise linear method with cascade amplification for signal processing on four bands in order to meet requirements for automatic observation of objects with large radiance differences (ocean color and land vegetation) exhibiting a wide dynamic range.

Table 3: GLI parameter specification

Figure 6: GLI image of Japan and east Asian countries (250 m resolution, 16 days composite, mosaic), image credit: Microwave Remote Sensing Laboratory

SeaWinds (NASA Scatterometer II), PI: M. Freilich, NASA/JPL. Objective: to acquire accurate, high-resolution, global measurements of sea-surface wind vectors in 1 to 2 day repeat cycles. Applications: studies of tropospheric dynamics and air-sea interaction processes, including air-sea momentum transfer. Improvement of weather forecasts near coastlines by using wind data in numerical weather- and wave-prediction models. SeaWinds consists of three major parts: SAS (SeaWinds Antenna Subsystem), SES (SeaWinds Electronics Subsystem), and CDS (Command and Data Subsystem). ^{14) 15)}

• SAS consists of a 1 m diameter parabolic reflector antenna mounted to a spin activator assembly, which causes the reflector to rotate at 18 rpm. The antenna spins at a very precise rate, and emits two beams about 6 degrees apart, each consisting of a continuous stream of pulses. The two beams are necessary to achieve accurate wind direction measurements. The pointing of these beams is precisely calibrated before launch so that the echoes may be accurately located on the ground from space.

• SES is the heart of the scatterometer and it contains a transmitter, receiver and digital signal processor. It generates and sends high radio frequency (RF) waves to the antenna. The antenna transmits the signal to the Earth's surface as energy pulses. When the pulses hit the surface of the ocean it causes a scattering affect referred to as backscatter.

• The CDS is essentially a computer housing the software that allows the instrument to operate. It provides the link between the command center on the ground, the spacecraft and the scatterometer. It controls the overall operation of the instrument, including the timing of each transmitted pulse and collects all the information necessary to transform the received echoes into wind measurements at a specific location on Earth.

The instrument is an active microwave radar (a scanning pencil-beam scatterometer) with dual-beam, 40º and 46º look angle from nadir, conical scan 1 m diameter reflector (dish) antenna, operating in Ku-band at 13.402 GHz (110 W pulse at 189 Hz PRF). Measurement of wind speeds between 3-20 m/s to an accuracy of 2 m/s, wind vector directions to an accuracy of 20º. The dish antenna is rotated about the satellite nadir axis at 18 rpm. Data is collected in a continuous 1800 km swath, centered about nadir. Spatial resolution = 50 km; IFOV = ±52º from nadir; mass = 205 kg; power = 250 W; duty cycle = 100%; average data rate = 40 kbit/s; thermal operating range is 5-40ºC; pointing knowledge to 500 arcseconds. - SeaWinds data products consist of global multiazimuth normalized radar cross section measurements and 50-km-resolution ocean vector wind maps. ^{16) 17)}

Table 4: Overview of SeaWinds performance parameters

Figure 7: Illustration of the SeaWinds scatterometer (image credit: NASA/JPL)

See also the SeaWinds instrument description under QuikSCAT for more details.

ILAS-II (Improved Limb Atmospheric Spectrometer-II), the sensor is of ILAS heritage on ADEOS, funded by MOE (Ministry of the Environment). The spectrometer uses gratings for solar occultation measurements of polar stratospheric ozone, atmospheric trace gases (O₃, HNO₃, NO₂, N₂O, CH₄, H₂O, CFC-11, CFC-12, ClONO₂, etc.), aerosols, temperature and pressure. ILAS-II is used to monitor and study changes in the stratosphere which are triggered by emissions of CFC gases. ^{18) 19) 20) 21)}

The instrument consists of the following elements: a two-axis gimbal mirror which is controlled to track the radiometer center of the sun, a 13 cm diameter Cassegrain telescope, beam splitters, and reflective transfer optics, three IR spectrometers, a VIS spectrometer, a sun-edge sensor, and signal processing units. The band 1 and 2 spectrometers employ a Czerny-Turner type spectrograph design with a plane grating in 30 gr./mm for band 1; the detector material for both bands is PbTiO₃. The band 3 spectrometer employs an echelle grating with 23.2 gr./mm. The VIS spectrometer uses a holographic concave grating (f/8.0, f=400 mm, 1800 lines/mm) with a 1024 pixel MOS photo diode array detector. The VIS spectrometer is self-calibrating using the information on the solar Fraunhofer lines. Instrument spectral coverage: 3-12.85 µm and 753-784 nm, spatial coverage = 10 - 60 km, vertical resolution = 1 km, observation accuracy = 5% (1% for ozone). The prime contractor for ILAS-II is MEI (Matsushita Electric Industrial Co. Ltd.).

Table 5: ILAS-II instrument parameters

Figure 8: Schematic view of the ILAS-II instrument (image credit: JAXA)

POLDER-2 (Polarization and Directionality of the Earth's Reflectances), passive optical imaging radiometer of CNES. The instrument is an identical twin to its predecessor, POLDER-1 flown on ADEOS. By simultaneously observing the Earth's radiation in polarized light and from different viewing angles, it is focusing on several themes. POLDER's very wide field of view is also a unique asset for building up time series of measurements from space, making it possible to obtain daily global coverage. POLDER-2 acquires also ocean color measurements. - The POLDER instrument is an imaging system, a radiometer/polarimeter, featuring a 2-D CCD detector array, wide field of view telecentric optics and a rotating wheel carrying spectral and polarized filters. The instrument spectral characteristics are defined in Table 6 (see also instrument description under ADEOS).

The POLDER-2 instrument has a mass of 32 kg, a size of about 800 mm x 500 mm x 250 mm, and a power consumption of 42 W.

Table 6: Spectral characteristics of POLDER

Figure 9: Schematic view of the POLDER-2 instrument (image credit: NASDA)

DCS (Data Collection System), a NASDA/CNES joint development (CNES-NASDA agreement as of 1996) referred to as Argos-Next. The DCS offers worldwide capabilities for location and environmental data collection for fixed and moving platforms. The downlink frequency of 460-470 MHz with a data rate of 200 bit/s is added to the existing Argos system. The received frequency of the DCP (Data Collection Platform) is 401.65 MHz, the data rate of the DCP = 400 bit/s. Total DCS instrument mass = 76 kg, power consumption = 60 W.

The Argos-Next instrument version offers a two-way messaging capability for enhanced service provision. So-called PMTs (Platform Messaging Transceivers) are being used by the ground segment platforms able to receive and interpret messages sent by the satellite. The new service spectrum permits for example to calibrate platform sensors and to manage duty cycle by switching terminals on and off when needed. Argos-Next also supports secure message transmissions. ^{22) 23)}

Table 7: Some DCS characteristics

2) http://sharaku.eorc.jaxa.jp/ADEOS2/index.html

3) ADEOS-II Reference Handbook, URL: http://sharaku.eorc.jaxa.jp/ADEOS2/doc/pdf/refbook_e_ver3.pdf

4) http://www.eorc.jaxa.jp/hatoyama/adeos2/gli_reprocessing_e.html

5) Operational Anomaly with Midori-II, Oct. 25, 2003, JAXA, URL: http://www.jaxa.jp/press/2003/10/20031025_midori2_e.html

6) Successful Intersatellite Communication Experiment Between Midori II (ADEOS-II) and ESA's ARTEMIS," URL: http://www.jaxa.jp/press/nasda/2003/midori2-artemis_20030404_e.html

7) http://sharaku.eorc.jaxa.jp/ADEOS2/sensor/sensor.html#ams

8) K. Imaoka, T. Sezai, T. Takeshima, T. Kawanishi, A. Shibata, "Instrument characteristics and calibration of AMSR and AMSR-E," Proceedings of IGARSS 2002, Toronto, Canada, June 24-28, 2002

9) M. Nakajima, Y. Ito, H. Maejima, Y. Kojima, "The Development of AMSR and GLI for ADEOS-II," presented at the 45^th Congress of the International Astronautical Federation, October 9-14, 1994, Jerusalem, Israel

10) T. Y. Nakajima, et al., "Optimization of the Advanced Earth Observing Satellite II Global Imager channels by use of radiative transfer calculations," Applied Optics, Vol. 37, No. 15, May 20, 1998, 3149-3163

11) T. Y. Nakajima, T. Nakajima, H. Masunaga, A. Higurashi, Y. Liu, "Cloud and aerosol retrievals from ADEOS/GLI and other sensors," Proceedings of IGARSS 2002, Toronto, Canada, June 24-28, 2002

12) F. Sakaida, K. Hosoda, M. Moriyama, H. Murakami, A. Mukaida, H. Kawamura, " Sea surface temperature observation by Global Imager (GLI)/ADEOS-II: Algorithm and accuracy of the product," Journal of Oceanography, Vol. 62, No 3, June 2006, pp. 311-319

13) R. Höller, A. Higurashi, Te. Nakajima, "The GLI 380 nm channel - application for satellite remote sensing of tropospheric aerosol," URL: http://www.eumetsat.int/Home/Main/Publications/Conference_and_Workshop_Proceedings/groups/cps/documents/document/pdf_conf_p41_s2_hoeller_v.pdf

14) http://science.hq.nasa.gov/missions/satellite_16.htm

15) http://winds.jpl.nasa.gov/missions/seawinds/index.cfm

16) M. W. Spencer, C. Wu, D. G. Long, "Tradeoffs in the Design of a Spaceborne Scanning Pencil Beam Scatterometer: Application to SeaWinds," IEEE Transactions on Geoscience and Remote Sensing, Vol. 35, No 1, Jan. 1997, pp. 115-120

17) B. D. Boller, et al., "The Development of the SeaWinds Scatterometer Electronics Subsystem (SES)," Proceedings of IGARSS'96, Vol. 1, pp. 269-272

18) Information provided by Y. Sasano of NIES (National Institute for Environmental Studies)

19) Y. Sasano, et al., "ILAS-II Instrument and Data Processing System for Stratospheric Ozone Layer Monitoring", Proceedings of SPIE, Vol.4150, pp.106-114, 2001

20) http://www-ilas2.nies.go.jp/en/

21) S. Oshchepkov, Y. Sasano, T. Yokota, N. Uemura, H. Matsuda, Y. Itou, H. Nakajima, "Simultaneous stratospheric gas and aerosol retrievals from broadband infrared occultation measurements," Applied Optics, Vol. 44, Issue 22, 2005, pp. 4775-4784

22) C. Gal, Argos-Next - Two-way messaging for enhanced service," CNES Magazine No 15, April 2002, p. 39

23) "Argos-Next gets to work," CNES Magazine No 18, Feb. 2003, p. 8