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ADEOS II
ADEOS II
ADEOS II
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ADEOS II
Illustration of ADEOS II
NamesAdvanced Earth Observing Satellite II
Midori II
ADEOS 2
Mission typeEarth observation
Environmental monitoring
OperatorNASDA
COSPAR ID2002-056A Edit this at Wikidata
SATCAT no.27597
Mission duration5 years (planned)
10 months and 9 days (achieved)
Spacecraft properties
BusADEOS
ManufacturerMitsubishi Electric Corporation
Launch mass3,680 kg (8,110 lb)
Payload mass1,300 kg (2,900 lb)
Dimensions6 × 4 × 4 m (20 × 13 × 13 ft)
Power5.3 kW
Start of mission
Launch date14 December 2002, 01:31 UTC
RocketH-IIA 202
Launch siteTanegashima Space Center, Yoshinobu 1
ContractorMitsubishi Heavy Industries
End of mission
Last contact23 October 2003, 23:55 UTC
Orbital parameters
Reference systemGeocentric orbit[1]
RegimeSun-synchronous orbit
Perigee altitude806 km (501 mi)
Apogee altitude807 km (501 mi)
Inclination98.70°
Period101.00 minutes
Instruments

ADEOS II (Advanced Earth Observing Satellite 2) was an Earth observation satellite (EOS) launched by NASDA,[2] with contributions from NASA and CNES, in December 2002.[3] and it was the successor to the 1996 mission ADEOS I. The mission ended in October 2003 after the satellite's solar panels failed.[4]

Mission overview

[edit]

The three primary objectives of the mission, as identified by NASDA, were to:[5]

  • Regularly monitor the water and energy cycle as a part of the global climate system
  • Quantitatively estimate the biomass and fundamental productivity as a part of the carbon cycle
  • Detect trends in long term climate change as a result of continuing the observations started by ADEOS I

The project had a proposed minimum life of three years, with a five-year goal.[6]

Instruments

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Annotation of ADEOS II and its instruments

The satellite was equipped with five primary instruments: Advanced Microwave Scanning Radiometer (AMSR), Global Imager (GLI), Improved Limb Atmospheric Spectrometer-II (ILAS-II), Polarization and Directionality of the Earth's Reflectances (POLDER), and SeaWinds. These instruments were designed to monitor Earth's water cycle, study biomass in the carbon cycle, and detect trends in long-term climate change. The mission was established to continue the work undertaken by ADEOS I between 1996 and 1997.[6][7]

Advanced Microwave Scanning Radiometer (AMSR)

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AMSR monitors water vapor, precipitation, sea surface, wind, and ice by means of microwave radiation emanating from Earth's surface and atmosphere. It is a radiometer that operates in eight frequency bands covering 6.9 GHz to 89 GHz, and monitors the horizontal and vertical polarizations separately. With a dish of 2 m (6 ft 7 in) aperture, the spatial resolution is 5 km (3.1 mi) in the 89 GHz band, degrading to 60 km (37 mi) at 6.9 GHz.[8]

Global Imager (GLI)

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GLI (GLobal Imager) is an optical sensor to observe solar radiation reflected from Earth's surface and map vegetation, clouds, etc. The data is acquired in 23 visible/near-infrared, and in 13 far infrared channels. The scanning is done by a rotating mirror covering 12 km (7.5 mi) along track and 1,600 km (990 mi) cross-track, and at a resolution of 1 km (0.62 mi). [9]

Improved Limb Atmospheric Spectrometer 2 (ILAS-2)

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ILAS-2 maps the vertical distribution of O3, NO2, HNO3, H2O, CFC-11, CFC-12, CH4, N2O, and ClONO2, as well as the distribution of temperature and pressure, all in the stratosphere. It observes the absorption spectrum in Earth's atmospheric limb in the 3-13 micron wavelength band, and in the 753-784 nm band of the occulting Sun. The altitude resolution is 100 m (330 ft).[10]

Polarization and Directionality of Earth's Reflectances (POLDER)

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POLDER measures the polarization, and spectral characteristics of the solar light reflected by aerosols, clouds, oceans and land surfaces. Eight narrow band wavelengths (443, 490, 564, 670, 763, 765, 865, and 910 nm) are covered by the instrument which enables identification of the physical and optical properties of the aerosols and their role in radiation budget.[11]

SeaWinds

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SeaWinds is a scatterometer that provides wind speed and direction by observing the microwave reflection from ocean surfaces. With its 1 m (3 ft 3 in) dish, it scans the surface along conical surfaces at 18 RPM. It provides speed at an accuracy of 2 m/s, wind direction at an accuracy of 20°, both with a spatial resolution of 5 km (3.1 mi).[12]

Subsystems

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In addition to the five main instruments, nine avionic subsystems were allocated to the bus module. These were the Communication and Data-Handling Subsystem (C&DH), Inter-Orbit Communication Subsystem (IOCS), Mission Data Processing Subsystem (MDPS), Optical Data Recorder (ODR), Electrical Power Subsystem (EPS), Paddle Subsystem (PDL), Attitude and Orbit Control Subsystem (AOCS), Reaction Control Subsystem (RCS), and the Direct Transmission Subsystem (DTL).[2]

The C&DH subsystem received and decoded the satellite's tracking control command signals and acted as a processing interface between the instruments. It was capable of adjusting settings on the instruments – such as temperature and voltage. The IOCS was used to communicate with data relay satellites (see Data transfer).[2]

The MDP device formatted mission data to be sent via the IOCS, and would process it into a data packet. The ODR was a large-volume storage device that used an optical magnetic disk system. The EPS provided power to the satellite's subsystems. The PDL managed the satellite's solar panel, and transferred electrical energy to the EPS. The solar panel was capable of generating 5 kW using 55,680 solar cells on a jointed mast.[2]

The AOCS was used to establish the attitude control following the satellite's deployment from the launch vehicle. It was subsequently used to adjust the satellite's attitude, orbit, and solar paddle. The AOCS was equipped with a number of attitude sensors, including a control-standard unit (IRC), an Earth sensor (ESA), and a fine Sun sensor assembly (FSSA).[2]

The RCS was used to generate propulsion power for attitude adjustments after deployment and control orbit using data from the AOCS.[2]

Data transfer

[edit]

ADEOS II transferred data to and from Artemis and the Data Relay Test Satellite (DRTS). The Artemis connection transferred information over a 26 GHz Ka-band link (for payload data) and a 2 GHz S-band link (for telemetry, tracking and control data).[2]

These signals were then downlinked to the Earth Observation Center (EOC) via feeder link stations and the Redu Station. ADEOS II also sent mission data directly to NASA stations, which routed information to bodies such as the EOC and sensor-providing organisations.[2]

Launch

[edit]

The mission was originally scheduled to launch aboard a H-II launch vehicle in February 2002. This was postponed as the Japanese Space Activities Commission would not launch without having three successful missions aboard the new H-IIA launch vehicle.[13]

The satellite was successfully launched from Tanegashima Space Center pad YLP-1 on 14 December 2002, aboard H-IIA 202.[14] Other payloads onboard included the Japanese MicroLabsat and WEOS microsatellites, as well as the Australian FedSat.[15]

Failure

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On 23 October 2003, the solar panel failed. At 23:49 UTC, the satellite switched to "light load" operation due to an unknown error. This was intended to power down all observation equipment to conserve energy. At 23:55 UTC, communications between the satellite and the ground stations ended, with no further telemetry received.[4] Further attempts to procure telemetry data on 24 October 2003 (at 00:25 and 02:05 UTC) also failed.[16]

Investigation

[edit]

After the power failure, JAXA formed the Midori II anomaly investigation team. Analysis of data received before transmissions ceased showed that the solar panel's power output had decreased from 6 kW to 1 kW. The investigation team began surveying the mission to establish whether the failure was due to a technical malfunction or a solar flare.[4]

One hypothesis was that debris had impacted the satellite's power harness between the solar array and the satellite bus. The harness was a core of wires enclosed in multi-layer insulation. The debris impact was theorised to have caused an electric arc,[2] which is an example of the spacecraft charging effect.[17]

The mission officially ended at the end of October 2003, with JAXA conceding that the "possibility of restoring the operations of Midori II [was] extremely slim". The mission, which had cost approximately 70 billion Yen (US$570 million)[15] was only able to recoup an estimated 300 million Yen through insurance.[4]

References

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ADEOS II

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from Grokipedia
ADEOS II, also known as Midori 2, was a Japanese Earth observation satellite developed by the Aerospace Exploration Agency (, formerly NASDA) as the successor to ADEOS I, designed to monitor global environmental changes including climate patterns, the water and energy cycles, ocean biology, and atmospheric ozone layers through advanced instruments. Launched on December 14, 2002, from aboard an rocket, it operated in a sun-synchronous subrecurrent at approximately 803 km altitude with a 99-degree inclination, enabling recurrent observations every four days. The mission was an international collaboration involving and France's , focusing on applications in climate research, , , and fisheries support. The satellite carried five primary Earth-observing instruments: the Advanced Microwave Scanning Radiometer (AMSR) for measuring sea surface temperatures, , and ; the Global Imager (GLI) for studying vegetation, ocean color, and aerosols; SeaWinds, a NASA-provided for mapping ocean wind vectors and weather patterns; the Improved Limb Atmospheric Spectrometer-II (ILAS-II) for profiling stratospheric and trace gases; and the Polarization and Directionality of the Earth’s Reflectances (POLDER-2) for analyzing Earth's radiation budget and cloud properties. Additionally, it included a (DCS) to relay environmental from ground-based platforms. These sensors collectively provided comprehensive on carbon, , and cycles, contributing to studies despite the mission's short duration. ADEOS II's operations ended prematurely on October 24, 2003, after just 10 months, due to a power failure caused by arcing in the solar array harness, attributed to spacecraft charging, which halted data collection and led to the loss of communication by October 31. Despite its early termination, the mission delivered valuable datasets that advanced understanding of environmental phenomena, such as sea surface winds and ozone depletion, and supported ongoing international Earth science efforts.

Mission Background

Development History

The Advanced Earth Observing Satellite II (ADEOS II), also known as Midori II, originated as a successor to the original ADEOS mission launched by Japan's National Space Development Agency (NASDA, now part of ) in August 1996, which provided valuable data for nearly a year before failing in June 1997 due to a power system malfunction. NASDA initiated planning for ADEOS II in the late as part of its broader ADEOS program to advance global environmental monitoring, focusing on climate, ocean, and atmospheric studies following the partial success of ADEOS I. Key development milestones began with the issuance of the ADEOS Series Research Announcement in January 1997, inviting international proposals for instrument utilization and scientific research, with a submission deadline in April 1997 and selected research teams starting work in August 1997. The project received formal approval from NASDA and Japan's Ministry of the Environment for fiscal year 2000, emphasizing ozone layer monitoring via the ILAS-II instrument, with spacecraft assembly led by Mitsubishi Electric Corporation drawing on lessons from ADEOS I. Integration of international instruments progressed through the early 2000s, culminating in pre-launch completion by late 2002, though the initial target launch date of 1999 was postponed to December 2002 aboard an H-IIA rocket from Tanegashima Space Center. International collaborations were central to ADEOS II's development, with NASDA serving as the primary lead in while partnering with the U.S. National Aeronautics and Space Administration () for the SeaWinds , developed by NASA's at a cost of $154 million including operations. France's Centre National d'Études Spatiales () provided the POLDER-2 instrument for aerosol and cloud observation, and Japan's Environment Agency contributed to the ILAS-II for atmospheric profiling. These partnerships, aligned with global initiatives like the World Climate Research Programme, ensured diverse sensor capabilities but required extensive coordination for integration and calibration. Development faced challenges, including delays stemming from the analysis of ADEOS I's failure, which shared similar designs and prompted enhancements in redundancy and reliability to mitigate power risks. This analysis influenced ADEOS II's bus design, incorporating improved fault-tolerant systems, though it extended the timeline beyond the original 1999 goal and the revised June 2000 target.

Objectives and Scope

The ADEOS II mission, launched by Japan's National Space Development Agency (NASDA, now part of the Aerospace Exploration Agency ()), aimed to advance by providing continuous observations of 's carbon and water cycles, climate variability, and atmospheric composition, thereby supporting international research on . These core goals built upon the foundational objectives of its predecessor, ADEOS I, but expanded to emphasize quantitative assessments essential for understanding interactions within the system. The mission's scope encompassed targeted monitoring of key environmental parameters, including ocean surface winds and temperatures to track heat exchange and circulation patterns, land vegetation mapping for assessing and productivity, ozone layer profiling to evaluate stratospheric depletion trends, and studies of aerosols and clouds to analyze their roles in and air quality. These efforts were designed to contribute geophysical data products that enhance models of biological and physical processes, such as estimation and distributions, without delving into specific measurement techniques. ADEOS II was planned for a nominal mission duration of three years, operating in a at approximately 803 km altitude with a 99° inclination and a 101-minute , enabling about 14 orbits per day for consistent global coverage at a local of 10:30. This configuration supported interdisciplinary by integrating data into major global programs, including the Global Energy and Water Cycle Experiment (GEWEX), the Global Observations of Forest Cover and Land Dynamics (GOFC-GOLD), and the Integrated Global Observing Strategy (IGOS).

Spacecraft Design

Bus and Core Subsystems

The ADEOS II spacecraft featured a modular bus design consisting of a mission module for instruments and a bus module housing core avionics, structured as a rectangular prism with dimensions of approximately 6 meters in length, 4 meters in width, and 4 meters in height when including appendages. This configuration represented an upgraded version of the ADEOS I platform, incorporating enhanced redundancy in critical subsystems to improve reliability for the planned three-year mission lifetime. The total launch mass reached 3,680 kg, enabling deployment into a at around 800 km altitude. Core subsystems supported autonomous operations and environmental resilience. The command and data handling (C&DH) subsystem utilized an onboard computer to manage command reception and decoding via a 2 GHz band, telemetry editing for status parameters like and voltage, instrument control, and for weekly operational plans. Thermal control was achieved through a combination of heaters, radiators, and passive elements to maintain component stability across orbital conditions, ensuring operational integrity for the bus and attached modules. The propulsion subsystem employed a (RCS) with hydrazine-fueled 1 N and 20 N thrusters for maintenance maneuvers and attitude adjustments, provisioned with fuel sufficient for five years of operations. Telemetry and tracking integrated S-band communications for housekeeping data transmission and command uplink, with rates supporting real-time monitoring, alongside Ka-band and X-band for higher-volume data relay when interfaced with external systems. Attitude determination relied on a three-axis strapdown system incorporating an inertial reference unit with gyroscopes, Earth sensors, fine sun sensors, and GPS receivers to achieve pointing accuracy better than 0.3 degrees. The deployed solar array spanned approximately 24 meters, generating over 5 kW of power at end-of-life to support these subsystems.

Power and Attitude Control Systems

The power system of ADEOS II was designed to provide reliable for its Earth observation instruments and subsystems during its . It featured two deployable solar array paddles constructed with (GaAs) solar cells, arranged in 50 flexible blankets containing 55,680 cells total, mounted on a 24-meter extendible mast for optimal sun exposure. These panels generated up to 5 kW of power at end-of-life conditions, sufficient to support the satellite's peak demands while accounting for degradation over the mission lifetime. For periods of or peak load, the system included nickel-hydrogen (Ni-H2) batteries to store and supply as needed. Power distribution occurred via a 28 V DC bus, managed by the electrical power subsystem (EPS), which handled regulation, battery charge/discharge cycles, and allocation to onboard components, incorporating dual buses for enhanced reliability against single-point failures derived from lessons of the predecessor ADEOS I mission. The attitude and control subsystem (AOCS) employed three-axis stabilization with zero-momentum control to maintain precise orientation relative to , essential for nadir-pointing instruments like the Global Imager and SeaWinds. Primary actuation was provided by four assemblies (RWAs) for fine adjustments in roll, pitch, and yaw, supplemented by two magnetic torquers (MTQs) for desaturation and disturbance rejection using . Attitude determination integrated a GPS receiver (GPSR) with an inertial reference unit for high-precision , achieving knowledge accuracies of approximately 0.1° in roll, 0.08° in pitch, and 0.14° in yaw, which supported an overall nadir pointing accuracy of 0.1 degrees. was built in through backup sensors, including sensors and fine sun sensors, and dual-string configurations for critical AOCS electronics to ensure fault-tolerant operation. To optimize power collection, the solar arrays were equipped with solar array drive assemblies (SADAs) that enabled continuous sun-tracking via stepper motors and integrated position sensors, allowing independent rotation of each paddle relative to the spacecraft body for maximum efficiency across orbital phases. This mechanism, combined with the AOCS, facilitated seamless integration with the satellite's structural bus, ensuring stable power input without compromising attitude stability. Overall, these systems provided the robust foundation for ADEOS II's multi-instrument payload, drawing on proven designs while incorporating redundancies to mitigate risks identified in prior missions.

Instruments

Advanced Microwave Scanning Radiometer (AMSR)

The Advanced Scanning Radiometer (AMSR) was a passive instrument aboard the ADEOS II satellite, developed and provided by Japan's National Space Development Agency (NASDA, now part of ). It operated as a conically scanning, total-power system with dual polarization at most frequencies, designed to measure Earth's microwave emissions for deriving geophysical parameters related to the . The instrument featured eight frequencies ranging from 6.925 GHz to 89.0 GHz, enabling observations across a broad spectrum of bands to capture emissions from the surface and atmosphere. The AMSR's antenna was a 2-meter offset , the largest of its kind for a spaceborne at the time, which allowed for enhanced in global observations. It scanned conically at a 40 rpm rate with a nominal incidence angle of approximately 55°, directing the beam across the satellite's ground track to provide continuous coverage. This design facilitated the measurement of brightness temperatures, which served as the basis for retrieving parameters such as with an accuracy of ±0.04 m³/m³, sea surface salinity, precipitation rates over oceans, and vegetation water content. Additional derived products included , , atmospheric , cloud liquid water, snow water equivalent, and concentration, supporting applications in monitoring and . The instrument achieved a swath width of approximately 1,600 km, enabling near-global coverage in its . Spatial resolutions varied by frequency, ranging from about 5 km at 89.0 GHz to 60 km at 6.925 GHz, with the higher frequencies providing finer detail for features like structures while lower frequencies penetrated deeper into for and assessments. For example, the 6.925 GHz channel offered resolutions around 40 × 70 km, suitable for large-scale mapping, whereas the 89.0 GHz channel resolved details at 3 × 6 km for and detection. Calibration was performed using onboard references, including a hot load target at approximately 300 and a cold-sky mirror reflecting deep space at about 3 , applied at the start and end of each scan rotation. These internal methods were supplemented by vicarious techniques, leveraging known targets such as stable land surfaces or ocean areas to correct for instrumental drift and ensure accuracy within 1–2 across channels. The equivalent temperature difference ranged from 0.3 at lower frequencies to 1.8 at 50.3 GHz, maintaining reliable sensitivity for weak signals.

Global Imager (GLI)

The was a sophisticated aboard the ADEOS II , designed as a 36-channel multispectral pushbroom scanner for high-resolution Earth observations across visible, , shortwave , and wavelengths ranging from 0.38 to 12.0 μm. Developed by Japan's National Space Development Agency (NASDA, now part of ), it featured an off-axis with a 300 mm aperture to collect incoming radiation, coupled with linear detector arrays—typically comprising detectors for visible/ bands, for shortwave , and for bands—that enabled simultaneous imaging along the flight track while a scanning mirror provided cross-track coverage. GLI's core capabilities centered on deriving key environmental parameters through its spectral channels, including the normalized difference vegetation index (NDVI) for assessing global vegetation health and biomass, aerosol optical depth for monitoring atmospheric pollution and clarity (with target accuracy of 0.05 or 10%), cloud top height and optical thickness for weather and climate studies, and snow/ice extent and albedo for cryosphere analysis. The instrument's design prioritized frequent global coverage to support carbon cycle monitoring, ocean productivity estimation, and land surface process studies, building on the legacy of prior sensors like the Ocean Color and Temperature Scanner. With a swath width of 1600 km at , achieved spatial resolutions of 250 m for six high-priority visible and shortwave channels dedicated to detailed terrestrial and oceanic features, while the remaining 30 channels operated at 1 km resolution for broader thermal coverage, enabling efficient mapping of heterogeneous landscapes without excessive data volume. Operational modes included viewing for standard global surveys, as well as tilted configurations (±20° along-track) facilitated by the adjustable scanning mirror, which allowed for stereoscopic imaging, along-track angle observations to mitigate sun glint over , and enhanced temporal sampling in targeted regions. These modes, combined with continuous thermal acquisition during both day and night, supported a 4-day recurrent cycle for near-global revisit times.

Improved Limb Atmospheric Spectrometer 2 (ILAS-2)

The Improved Limb Atmospheric Spectrometer-II (ILAS-II), developed by Japan's Ministry of the Environment (MOE) and National Institute for Environmental Studies (NIES), was a solar occultation instrument designed for measuring vertical profiles of stratospheric trace gases and aerosols, primarily in polar regions, as part of ADEOS-II's contribution to atmospheric research. It featured four spectrometers: three infrared Fourier transform spectrometers and one visible grating spectrometer, utilizing a 13 cm Cassegrain telescope, beam splitters, a two-axis gimbal mirror for sun-tracking, a sun-edge sensor, and signal processing units. The infrared channels covered wavelengths from 3.0–5.7 µm (22 channels), 6.21–11.76 µm (44 channels), and 12.78–12.85 µm (22 channels), while the visible channel spanned 753–784 nm (1024 channels). Cryogenic cooling was provided by a Stirling-cycle mechanical cooler to maintain detector temperatures around 77 K, ensuring low noise for infrared detection. The instrument was mounted on the ADEOS-II spacecraft's mission module, oriented nadir-pointing in a sun-synchronous orbit to enable sunset and sunrise occultation observations. ILAS-II's capabilities centered on retrieving vertical profiles of key atmospheric constituents, including (O₃), (HNO₃), (NO₂), (N₂O), (CH₄), (H₂O), chlorine nitrate (ClONO₂), chlorofluorocarbons (CFC-11 and CFC-12), and extinction coefficients, along with and data up to 60 km altitude. It also detected polar stratospheric clouds (PSCs) and provided insights into distributions relevant to chemistry. Operations focused on high latitudes, covering 57–73°N and 64–88°S, with approximately 100 occultation events per day—derived from 14 orbits daily, each yielding multiple measurement points—to support studies of and stratospheric dynamics. These profiles contributed to broader mission objectives for monitoring global atmospheric composition changes, such as those driven by human activities. The instrument achieved a vertical resolution of approximately 1–1.5 km and a horizontal tangent resolution of 1.5–2 km in the visible channel, with infrared fields of view ranging from 13–21.7 km horizontally. This resolution enabled detailed profiling of thin stratospheric layers, surpassing the coarser capabilities of prior systems. ILAS-II represented an upgrade from the ILAS instrument on ADEOS-I, incorporating enhanced detector stability through improved cooling and signal-to-noise ratios, as well as additional infrared channels for better coverage of species like ClONO₂. These advancements addressed limitations in the original ILAS, such as spectral gaps and reduced precision in polar observations, allowing for more reliable data during ADEOS-II's operational period from to 2003.
ParameterSpecification
Channels3.0–5.7 µm (22 ch.), 6.21–11.76 µm (44 ch.), 12.78–12.85 µm (22 ch.)
Visible Channel753–784 nm (1024 ch.)
Vertical ProfilesO₃, HNO₃, NO₂, N₂O, CH₄, H₂O, ClONO₂, CFC-11, CFC-12, aerosols, , pressure
Altitude Range10–60 km
Daily Occultations~100 events (high latitudes)
Vertical Resolution1–1.5 km
Horizontal Resolution1.5–21.7 km (channel-dependent)

Polarization and Directionality of the Earth’s Reflectances (POLDER-2)

The Polarization and Directionality of the Earth’s Reflectances (POLDER-2) instrument on ADEOS II was a wide-field-of-view and developed by the French space agency (Centre National d'Études Spatiales). It utilized a two-dimensional (CCD) detector array with 274 × 242 pixels, paired with telecentric providing a of ±43° along-track and ±51° across-track, to capture reflected solar radiation from 's surface and atmosphere. A rotating wheel housed spectral filters and polarizers, enabling simultaneous measurements of intensity and polarization in multiple directions. POLDER-2 operated across nine spectral bands ranging from 0.443 µm to 0.910 µm, with bandwidths of 10–40 nm; these included six channels for total radiance (at 443, 490, 565, 670, 763/765, and 865/910 nm, where paired bands targeted oxygen and absorption) and three dedicated polarized channels (at 443, 670, and 865 nm) using 0°, 45°, and -45° polarizers. Bidirectional sampling was achieved passively through the satellite's orbital motion along its sun-synchronous path, allowing the same ground target to be observed sequentially from varying geometries without active scanning mechanisms. This design facilitated global coverage with a swath width of 1,800 km along-track by 2,400 km across-track and a nominal of 6 km × 7 km at . The instrument's core capabilities centered on polarimetric observations to quantify light scattering processes. It measured the (BRDF) to characterize how reflectance varies with illumination and viewing angles over , , and vegetation canopies. For atmospheric studies, POLDER-2 retrieved aerosol properties such as optical thickness, size distribution, and type by analyzing polarized signatures in the visible and near-infrared spectrum. In cloud microphysics, it assessed particle phase, effective radius, and through depolarization ratios and angular dependencies. Additionally, the multi-angular data enabled evaluation of bidirectional effects in vegetation, such as the "hot spot" phenomenon in plant canopies, aiding in structural and photosynthetic assessments. POLDER-2's viewing geometry provided up to 14 distinct angles per across its swath, depending on the target's position relative to the track, yielding comprehensive multi-angular polarization datasets for inverting models. This complemented the Global Imager (GLI) by supplying polarized corrections to improve surface reflectance accuracy in non-polarized multi-spectral observations.

SeaWinds

The SeaWinds instrument was an active microwave developed by NASA's (JPL) for the ADEOS II mission, operating in the Ku-band at 13.402 GHz to measure radar from Earth's surface. It featured a 1-meter-diameter dish antenna that rotated continuously at 18 revolutions per minute in a mode, employing dual pencil beams with incidence angles of 40° (inner, H- and V-polarized) and 46° (outer, V-polarized) relative to to illuminate the surface. This design enabled the collection of normalized radar cross-section (σ⁰) measurements across a wide swath, supporting vector wind retrievals through analysis of variations influenced by . SeaWinds provided high-precision measurements of near-surface ocean wind vectors, with speeds ranging from 3 to 20 m/s at an accuracy of better than 2 m/s and directions accurate to within ±20°; higher speeds up to 50 m/s could be detected with reduced accuracy. Beyond ocean winds, the instrument's sensitivity to surface dielectric properties and roughness allowed for applications in mapping, where differences between ice types and open water facilitated extent and concentration estimates; detection over land via variations in σ⁰ response to volumetric water content; and rain rate estimation over both ocean and land, as precipitation attenuates and scatters the signal, enabling rates up to several mm/h to be inferred. The instrument achieved a swath width of 1,800 km, with σ⁰ measurements resolved into approximately 2 km × 2 km cells along-track and cross-track, though wind vector products were typically binned to 25 km for ambiguity resolution. This spatial sampling supported near-global coverage of ice-free oceans every 2–3 days, contributing to and climate studies. Calibration was maintained through an internal precision loop using a noise source to monitor and correct for temperature-induced variations in the transmitter and receiver chains, achieving stability within 0.2 dB. Ground-based transponder networks provided external absolute by reflecting known signals back to the , ensuring σ⁰ accuracy across beams and orbits. These methods, combined with post-launch adjustments using natural targets like the , verified the instrument's performance throughout the mission.

Launch and Operations

Launch Sequence

ADEOS II, also known as Midori 2, with final preparations including environmental testing and mating to the launch vehicle completed without significant delays or weather-related postponements. The satellite launched on December 14, 2002, from the Yoshinobu Launch Complex at in , aboard an 202 rocket, marking the first successful flight of this specific configuration featuring the core stage augmented by two solid rocket boosters. Liftoff occurred at 01:31 UTC (10:31 JST) under clear conditions, with the vehicle ascending on an initial of 122 degrees to achieve a . The ascent sequence proceeded nominally: the solid rocket boosters ignited at T+0 seconds and separated at approximately T+125 seconds after burnout, followed by jettison around T+265 seconds to reduce mass. The first stage's LE-7A engine continued burning until main engine at roughly T+390 seconds, after which the second stage's LE-5B engine ignited to perform the orbital insertion burn. ADEOS II separated from the second stage at T+16 minutes 31 seconds, successfully injecting into a at 803 km altitude with an inclination of 98.6 degrees. Immediately following separation, ground stations acquired signals from the spacecraft, with initial confirmation received at the Tracking Station in approximately one hour post-liftoff at 11:33 JST. Deployment of the solar array paddles and other appendages was verified shortly thereafter, confirming the satellite's stable configuration in .

Orbital Configuration and Commissioning

ADEOS II was inserted into a following launch, with an altitude of approximately 803 km, an inclination of 98.6°, and an of 101 minutes. The orbit featured a local equator crossing time of 10:30 AM on the descending node and a 4-day subrecurrent cycle, enabling consistent daily observations of Earth's environmental parameters. Initial orbit adjustments were performed using the satellite's (RCS) thrusters, including 1 N and 20 N units, to fine-tune the parameters and achieve the final configuration. The commissioning phase spanned from December 2002 to March 2003, encompassing the initial checkout period (L+0 to L+3 months) during which critical systems were activated and verified. Immediately post-separation, the solar arrays were deployed via an ordnance deployment controller within the electrical power subsystem, generating over 5 kW to support subsequent operations. Attitude acquisition was established using a three-axis zero-momentum , incorporating sensors, Earth sensor assemblies, fine sun sensors, reaction wheels, and magnetic torquers, achieving pointing accuracy better than 0.3°. Ground contact was maintained every orbit through the tracking and control system, utilizing S-band uplinks/downlinks and direct links to Japanese stations at the Earth Observation Center (EOC), supplemented by international sites such as for data relay. Subsystem checkouts, including command and data handling (C&DH), attitude and orbit control (AOCS), and electrical power (EPS), confirmed nominal performance throughout the phase. Performance verification extended to inter-satellite communication tests, such as those with the satellite on March 28–30, 2003. Instruments underwent on-orbit calibration starting in early 2003, with solar-ray and internal-lamp methods applied to ensure accuracy; for example, the Advanced Microwave Scanning Radiometer (AMSR) completed brightness temperature calibration around day 40 post-launch in February 2003. First light images were acquired by January 2003, including AMSR observations on January 18 and Global Imager (GLI) images of a winter cyclone off Tohoku and the Kyushu Island region on January 25, validating initial sensor functionality. All subsystems operated nominally by the end of commissioning, paving the way for routine science data collection.

Data Management

Transmission Protocols

The ADEOS II satellite employed distinct frequency bands for downlink transmission to ensure efficient delivery of science and housekeeping data to ground stations. High-rate science data was transmitted via the X-band at rates up to 80 Mbps using QPSK modulation, supporting the bulk of instrument observations such as those from the Global Imager (GLI). In contrast, low-rate telemetry and tracking data utilized the S-band at 8–32 kbps, primarily for housekeeping information and command verification. Data transmission adhered to CCSDS-compliant packet standards, enabling structured and interoperable data flow from the satellite's onboard systems. This included Reed-Solomon error correction coding to mitigate transmission errors, ensuring during downlink. The system operated in both real-time modes, where data was sent immediately upon acquisition, and stored modes using the Mission Data Recorder (MDR) for playback during optimal passes. Daily science data volume averaged approximately 100 GB, with prioritization allocated to high-volume instruments like to maximize scientific return within orbital constraints. Command uplinks were secured through in the 2 GHz band, processed by the Command and Data Handling (C&DH) subsystem to prevent unauthorized access. Upon receipt, downlink data was packaged in (HDF) for ground processing and distribution.

Ground Receiving Stations

The ground receiving network for ADEOS II consisted of a combination of Japanese facilities and international stations to ensure global data acquisition and processing. The primary Japanese stations were the Space Center (TKSC) for satellite command, control, and tracking, and the Earth Observation Center (EOC) in Hatoyama, , which served as the central hub for data reception and initial processing. Overseas stations supplemented the network to achieve comprehensive coverage, particularly for X-band data transmission. The Kiruna station in , operated by the (SSC), acquired visible passes at a rate of 6 per day under operational agreements with . NASA's Alaska SAR Facility (ASF) in Fairbanks, , handled 10-11 passes daily, while the Wallops Flight Facility (WFF) in managed 3 passes per day; both transmitted processed data online to the EOC. Additionally, the Showa Station in received specialized Global Imager (GLI) data at 250-meter resolution. The chain began with raw Level 0 data collected at the EOC and overseas stations, where it underwent conversion to engineering values, radiometric, and geometric corrections to produce Level 1A products. Further at the EOC generated Level 1B data and higher-level products up to Level 2, incorporating geophysical parameters such as and content using validated algorithms. These products were archived and distributed through JAXA's Information System (EOIS) and international repositories, including NASA's Earthdata archives. The network supported the satellite's , enabling approximately 14 daily passes for global coverage with a 1,600 km swath width across instruments like AMSR and . International agreements facilitated instrument-specific data handling, including NASA's role in processing SeaWinds data and CNES's responsibility for Polarization and Directionality of the Earth's Reflectances () products, ensuring shared access for collaborative research.

Mission Failure

Anomaly Timeline

The ADEOS II mission proceeded nominally for approximately 10 months following its launch on December 14, 2002, successfully collecting a substantial volume of data during routine operations, including periodic sun-pointing maneuvers to optimize orientation. On October 24, 2003, at 23:49 UTC (corresponding to 8:49 a.m. JST on October 25), the satellite experienced an unexpected power drop, automatically switching to "light load" mode to conserve energy, with all observation instruments deactivating. At this point, solar array paddle output plummeted from approximately 6 kW to 1 kW, and ground controllers at the Center in noted the failure to receive scheduled data at 7:28 a.m. JST. The anomaly progressed rapidly the same day. By 8:55 a.m. JST on October 25 (23:55 UTC on October 24), communications became unstable, and telemetry data ceased to be received. Attempts from ground stations, including the Katsuura Tracking Station, to reestablish contact and reset systems failed, with no telemetry acquired by 9:23 a.m. JST and again at 11:05 a.m. JST. By October 25, 2003, the satellite had entered a full blackout state, placing it in safe hold mode with no instrument functionality or reliable communication possible. Ground teams issued commands to isolate potential faults and restore operations, but these efforts yielded no recovery, and final contact was lost shortly thereafter, marking the effective end of the mission. JAXA's anomaly investigation team, formed immediately, confirmed the irrecoverable nature of the failure by October 31.

Investigation Findings

Following the power anomaly detected on October 24, 2003, the Aerospace Exploration Agency () established the Midori-II anomaly investigation committee on October 25, 2003, to probe the failure of ADEOS II (also known as Midori-II). The committee included representatives from the National Space Development Agency of (NASDA, predecessor to ), the (), and the French Centre National d'Études Spatiales (), drawing on international expertise in satellite operations and environmental hazards. The investigation culminated in a comprehensive report detailing analysis, ground simulations, and environmental modeling to identify the root cause. The probable cause was identified as an arc discharge triggered by charging of ungrounded and the power harness bundle by auroral plasma particles, resulting in a catastrophic across 104 wire harnesses. This arcing propagated rapidly, severing electrical connections between the solar arrays and the , reducing power output from approximately 6 kW to 1 kW and rendering the inoperable. While no inherent design flaws were found, the investigation highlighted inadequate protection against environmental charging and debris, particularly in the satellite's polar orbit where auroral particles could accumulate on ungrounded surfaces. Contributing factors included heightened conditions during the peak of 23, with intense geomagnetic storms in October 2003 exacerbating plasma density in the auroral zones traversed by ADEOS II's 98.6° inclination . Additionally, cumulative wear from ten months of orbital exposure, including thermal cycling and repeated passages through charged environments, likely degraded the (MLI) on the high-voltage harnesses, increasing vulnerability to arcing. The investigation's recommendations emphasized preventive measures for future low Earth orbit missions, including enhanced electrostatic shielding and grounding for power systems to mitigate plasma interactions. These were directly applied to the Advanced Land Observing Satellite (ALOS), launched in 2006, which incorporated improved harness insulation and debris-resistant designs informed by ADEOS II's lessons. Furthermore, upgrades to onboard anomaly detection software were advised, enabling real-time monitoring of charging potentials and automatic safeguards against sustained arcs.

Scientific Impact

Key Data Contributions

The ADEOS II mission delivered approximately nine months of near-continuous data from to 2003, prior to the satellite's failure, resulting in global datasets archived across international repositories managed by JAXA's Center and NASA facilities such as the Alaska Satellite Facility and . Key instrument outputs included soil moisture maps from the Advanced Microwave Scanning Radiometer (AMSR), derived from multi-frequency brightness temperature measurements to estimate surface water content on a global scale at approximately 25 km spatial resolution. The Global Imager (GLI) produced vegetation indices, such as , and optical depth products at 250 m resolution for select visible/near-infrared bands, enabling detailed monitoring of and atmospheric particulates. The Improved Limb Atmospheric Spectrometer II (ILAS-II) generated vertical profiles through solar occultation, yielding 5,890 measurements spanning altitudes of 10–60 km in high-latitude regions (56°–70° N and 63°–88° S). The Polarization and Directionality of the Earth’s Reflectances (POLDER-2) instrument provided (BRDF) models across nine spectral bands (443–910 nm), facilitating analysis of surface and . SeaWinds data offered near-real-time ocean wind fields with speed accuracy of 2 m/s (for 3–20 m/s winds) and direction accuracy of 20°, at 25 km resolution, covering over 90% of ice-free oceans every two days. Post-mission processing enhanced data accessibility, with level-3 and level-4 products reprocessed using refined algorithms for improved geophysical parameter retrievals, distributed through agency portals. A distinctive contribution was the POLDER-2 multi-angular polarization dataset, which extended the pioneering global observations from ADEOS I and provided continuity to subsequent missions like NASA's Terra and Aqua, offering the most extensive space-based records of polarized reflectances for and studies at the time.

Research Applications and Legacy

The SeaWinds on ADEOS II provided high-resolution surface measurements that enhanced understanding of the and energy cycles in the global climate system, contributing to improved models for weather phenomena including tropical cyclones. Additionally, SeaWinds data enabled quantitative estimates of terrestrial and , supporting analyses of the and its role in global warming. The instrument advanced monitoring through high-resolution (250 m) classifications, such as those applied to in the Indochina Peninsula using International Geosphere-Biosphere Programme standards, which informed assessments of human-induced environmental changes. -derived annual global net estimates of 112.5 PgC/year aligned with ranges reported in the IPCC Third Assessment Report, providing a baseline for change evaluations spanning 1997–2003. The Improved Limb Atmospheric Spectrometer-II (ILAS-II) delivered validated vertical profiles of and related in high-latitude regions, aiding investigations into stratospheric dynamics and early trend analyses during the post-Montreal Protocol era. Combined datasets from these instruments facilitated carbon flux estimations, with ocean and SeaWinds data contributing to cycle modeling that improved accuracy in global assessments. ADEOS II's legacy influenced Japan's Global Change Observation Mission (GCOM) series, particularly through the succession of its sensors to instruments like the Advanced Microwave Scanning Radiometer 2 (AMSR2) on GCOM-W1, enabling long-term monitoring of water cycles and climate variables beyond the original mission's duration. ADEOS II data have supported numerous peer-reviewed publications in sciences, underscoring its role in advancing global environmental research. The mission's power system failure due to plasma-induced charging in auroral zones prompted to redesign satellite architectures, emphasizing enhanced charging mitigation in polar -orbiting platforms. ADEOS II fostered international collaboration in , exemplified by joint data processing with and , which strengthened protocols for global data dissemination and interoperability among agencies. Its 2003 observations complemented contemporaneous datasets from MODIS on Terra/Aqua and Envisat's instruments, filling temporal and spectral gaps in climate records for that year, particularly in and monitoring. Despite its abbreviated 10-month operational lifespan, ADEOS II's archived datasets, maintained by JAXA's Research Center, have sustained utility in reanalysis efforts, including 2020s studies on variability such as long-term snow/ice trends and when integrated with successor missions. This enduring accessibility highlights the mission's value in bridging short-term observations to decadal investigations, though the limited duration constrained continuous time-series development.

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