GCOM (Global Change Observation Mission), is a JAXA project of long-term observation of Earth environmental changes. As a part of Japan's contributions to

GEOSS The Global Earth Observation System of Systems (GEOSS) was built by the Group on Earth Observations (GEO) on the basis of a 10-Year Implementation Plan running from 2005 to 2015. GEOSS seeks to connect the producers of environmental data and decisi ...

(Global Earth Observation System of Systems), GCOM will be continued for 10 to 15 years with observation and utilization of global geophysical data such as precipitation, snow, water vapor, aerosol, for climate change prediction, water management, and

food security Food security speaks to the availability of food in a country (or geography) and the ability of individuals within that country (geography) to access, afford, and source adequate foodstuffs. According to the United Nations' Committee on World ...

. On May 18, 2012, the first satellite " GCOM-W" (nickname "Shizuku") was launched. On December 23, 2017, the second satellite "GCOM-C1" (nickname "Shikisai) was launched.

GCOM-W

GCOM-W (Global Change Observation Mission – Water "Shizuku") is the first in the GCOM series. Its mission is to observe the

water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...

. The satellite carries the AMSR2 (Advanced Microwave Scanning Radiometer 2) instrument, the successor to the AMSR-E carried by

Aqua Aqua is the Latin word for water. It is used in many words which relate to water, such as aquatic life. In English, it may also refer to: Arts * Aqua (color), a greenish-blue color Business * Aqua (skyscraper), an 82-story residential skysc ...

. This microwave radiometer will observe precipitation, water vapor, wind velocity above the ocean, sea water temperature, water levels on land areas, and snow depths. GCOM-W was approved in 2006, and development of the satellite started in 2007 with a mission budget of 20 billion Yen (US$200 Million). Mass of the satellite is 1990 kg. Planned lifespan is 5 years. Polar orbit (altitude 700 km) with equator crossing local time on the ascending orbit is 13:30PM +/- 00:15. GCOM-W was launched on May 17, 2012, via a

H-IIA rocket H-IIA (H-2A) is an active expendable launch system operated by Mitsubishi Heavy Industries (MHI) for the JAXA, Japan Aerospace Exploration Agency. These liquid fuel rockets have been used to launch satellites into geostationary orbit; lunar ...

, and it flies in a sun-synchronous orbit as part of the " A-train" satellite constellation. It successfully began collecting data on July 4, 2012. Its planned lifespan of 5 years means that the satellite is set to operate until 2017, although JAXA hopes that it will last longer.

GCOM-C1

GCOM-C1 (Global Change Observation Mission – Climate "Shikisai"), the first satellite in the GCOM-C series, will monitor global

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

by observing the surface and atmosphere of Earth over the course of 5 years. Through use of its SGLI (Second generation GLobal Imager) optical instrument, it will collect data related to the

carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...

and radiation budget, such as measurements of clouds, aerosols, ocean color, vegetation, and snow and ice. From its sun-synchronous orbit (altitude 798 km), SGLI will collect a complete picture of Earth every 2–3 days with a resolution of 250-1000m, across the UV, visible, and infrared spectrums. Mass of the satellite is 2020 kg. Equator crossing local time on the descending orbit is 10:30AM +/- 00:15. GCOM-C was launched on December 23, 2017, via a

Sensors

AMSR2

AMSR2 (Advanced Microwave Scanning Radiometer 2) is an improved version of AMSR (aperture 2.0 m) on

ADEOS II ADEOS II (Advanced Earth Observing Satellite 2) was an Earth observation satellite (EOS) launched by NASDA, with contributions from NASA and CNES, in December 2002. and it was the successor to the 1996 mission ADEOS I. The mission ended in Oc ...

and AMSR-E (aperture 1.6 m) on NASA's

satellite. By rotating a disc antenna (diameter 2.0 m) in 1.5 s period, it scans the Earth surface along an arc of 1450 km length. Reliability is better than AMSR and AMSR-E. Planned lifetime has been extended from 3 years to 5 years. A new microwave band, namely 7.3 GHz, has been added. The 7.3 GHz band is for duplication and calibration of 6.925 GHz band. AMSR2 continues the legacy of AMSR-E, which also observed as part of the A-Train constellation. Note: ◎ means the most important band for that purpose.

SGLI

SGLI (Second-generation Global Imager) is a multi-band optical radiometer and the successor of GLI sensor on

ADEOS-II ADEOS II (Advanced Earth Observing Satellite 2) was an Earth observation satellite (EOS) launched by NASDA, with contributions from NASA and CNES, in December 2002. and it was the successor to the 1996 mission ADEOS I. The mission ended in Oct ...

. It consists of two sensors: SGLI-VNR (an electronic scan) and SGLI-IRS (a mechanical scan). SGLI-VNR succeeds the technology of MESSR on MOS-1, OPS/VNIR on

JERS-1 Japanese Earth Resources Satellite 1 (JERS-1) was a satellite launched in 1992 by the National Space Development Agency of Japan (NASDA, now part of JAXA). It carried three instruments: *An L-band (HH polarization) synthetic aperture radar (SAR); * ...

, AVNIR on

ADEOS ADEOS I (Advanced Earth Observing Satellite 1) was an Earth observation satellite launched by NASDA in 1996. The mission's Japanese name, Midori means "green". The mission ended in July 1997 after the satellite sustained structural damage to th ...

, and AVNIR-2 on

ALOS Advanced Land Observing Satellite (ALOS), also called Daichi (a Japanese word meaning "land"), is a 3810 kg Japanese satellite launched in 2006. After five years of service, the satellite lost power and ceased communication with Earth, but ...

. The number of channels of SGLI is 19, which is much less than GLI (36 channels). This is because SGLI carefully selected the essential bands for observations. The swath size is 1150 km for SGLI-VNR and 1400 km for SGLI-IRS. Although a little reduction from GLI (all channels were mechanical scan with 1400 km swath), it has more bands with high-resolution (250 m). Polarimetry function has been added to SGLI-VNR, which helps detection of size of aerosol particles, enabling detection of source of the aerosols. The lesson of GLI sensor's too big and too complicated structure, SGLI is divided to two simple systems, and the number of channels have been minimized to really essential bands, aiming at better reliability and survivability.

References