NASA's Aqua spacecraft
by Claire Parkinson, Aqua Project Scientist
June 24, 2002

 

Introduction

The Aqua mission builds on NASA's long history of studying the Earth and its atmosphere from the impressive perspective of space. NASA scientists and others have been doing such studies since the 1960s, and the efforts by now have matured to the point where many Earth science elements are being studied together as a global system. Earth System Science integrates several important scientific disciplines, including meteorology, atmospheric chemistry, oceanography, glaciology, hydrology, and biology. Amongst the aims are an integrated understanding of the Earth system at present, an improved understanding of the prominent changes the system has undergone in the past, and improved predictions regarding how the system is likely to change in the future. Satellites contribute toward these goals by enabling the collection of global data sets that would be impractical through any other available means.

Aqua spacecraft image

The Aqua satellite. (Image courtesy of Reto Stockli, based on an image from TRW).

next: Aqua Goals

 

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Aqua

Introduction
Aqua Goals
Mission Facts
Aqua Animations

Aqua First Light Images


 

NASA's Aqua spacecraft
 

 

Aqua Goals

The Aqua spacecraft, and more broadly the Earth Observing System (EOS) of which Aqua is a part, continues NASA's commitment to studying the Earth as a global system. Aqua carries six state-of-the-art instruments to observe the Earth's oceans, atmosphere, land, ice and snow covers, and vegetation, providing high measurement accuracy, spatial detail, and temporal frequency. This comprehensive approach, provided by both Aqua and the earlier Terra satellite launched in December 1999, enables scientists to study interactions among the many elements of the Earth system.

Aqua, Latin for "water," is named for the large amount of information that the Aqua spacecraft will collect about the Earth's water cycle. In particular, the Aqua data will include information on water vapor and clouds in the atmosphere, precipitation from the atmosphere, soil wetness on the land, glacial ice on the land, sea ice in the oceans, snow cover on both land and sea ice, and surface waters throughout the world's oceans, bays, and lakes. Such information will help scientists to improve the quantification of the global water cycle and to examine such issues as whether or not the cycling of water might be accelerating.

Schematic of Hydrologic Cycle

In the hydrologic cycle, individual water molecules travel between the oceans, water vapor in the atmosphere, water, ice, and snow on the land, and underground water. (Image by Hailey King.)

In addition to information about the water cycle, Aqua will also provide information on many additional elements of the Earth system. For instance, Aqua will enable studies of the fluxes of radiation from the sun and from the Earth that combine to constitute the Earth's radiation balance. It will also enable studies of small particles in the atmosphere termed "aerosols" and such trace gases in the atmosphere as ozone, carbon monoxide, and methane. The trace gases each have a potential contribution to global warming, whereas the aerosols are more likely to have a cooling effect. Aqua will also provide observations on vegetation cover on the land, phytoplankton and dissolved organic matter in the oceans, and the temperatures of the air, land, and water. All of these measurements will have the potential to contribute to improved understanding of the changes occurring in the global climate and the role of the interactions among the various elements of the climate system.

One of the most exciting of the potential practical benefits likely to derive from the Aqua data is improved weather forecasting. Aqua carries a sophisticated sounding system that will allow determination of atmospheric temperatures around the world to an accuracy of 1° Celsius in 1-kilometer-thick layers throughout the troposphere, the lowest portion of the atmosphere. The troposphere extends to an altitude of about 10-15 kilometers, depending on location, and contains most of the global cloud cover. The anticipated 1° Celsius accuracy far exceeds current accuracies from satellite observations and, in conjunction with the moisture profiles also obtainable from the Aqua sounding system, will offer the potential of improved weather forecasting. NASA is working with the U. S. National Oceanic and Atmospheric Administration, the European Centre for Medium-Range Weather Forecasts, and other forecasting centers to facilitate the incorporation of the Aqua data in their weather forecasting efforts.

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back: Introduction

 

pullquote

Aqua

Introduction
Aqua Goals
Mission Facts
Aqua Animations

Aqua First Light Images


 

NASA's Aqua spacecraft
 

 

Mission Facts

Aqua is a joint project among the United States, Japan, and Brazil. The U.S. provided the spacecraft and the following four instruments: the Atmospheric Infrared Sounder (AIRS), the Clouds and the Earth's Radiant Energy System (CERES), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Advanced Microwave Sounding Unit (AMSU). Japan's National Space Development Agency (NASDA) provided the Advanced Microwave Scanning Radiometer for EOS (AMSR-E); and Brazil's Instituto Nacional de Pesquisas Espaciais (INPE, the Brazilian Institute for Space Research) provided the Humidity Sounder for Brazil (HSB).

Overall management of the Aqua mission is located at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Goddard also provided the MODIS and AMSU instruments, managed the integration and testing of the spacecraft, is operating the spacecraft, and is receiving, processing, and (eventually) disseminating much of the science data through the EOS Data and Information System (EOSDIS). Goddard manages EOS for NASA's Earth Science Enterprise, headquartered in Washington, D.C. NASA's Jet Propulsion Laboratory, Pasadena, California, provided the AIRS instrument; and NASA's Langley Research Center, Hampton, Virginia, provided two CERES instruments, which will allow coincident measurements by one CERES scanning in lines perpendicular to the path of the satellite and by the other CERES scanning in lines at various angles with respect to the satellite's path. TRW constructed the Aqua spacecraft and carried out, at its facilities in Redondo Beach, California, the spacecraft's integration and testing.

Aqua was launched on May 4, 2002 at 2:55 a.m. PDT aboard a Delta II 7920-10L launch vehicle from the Western Test Range of Vandenberg Air Force Base, California. NASA's Kennedy Space Center, Florida, was responsible for the launch operations, including the Delta launch vehicle and the pre-launch integrated processing facility, the former under a contract with the Boeing Company and the latter under a contract with Spaceport Systems International. The U.S. Air Force was responsible for all range-related matters.

Delta rocket launch image

Aqua was launched aboard a Delta 7920-10L rocket at 2:55 a.m. PDT on May 4, 2002. View a 1-minute launch sequence video (1 MB Quicktime .mov) (Photo courtesy of NASA/Bill Ingalls; video courtesy of Vandenberg Air Force Base, digitized by Vicky Weeks, NASA GSFC).

During launch, Aqua ascended to an altitude of 680 kilometers, after which it was boosted to its final orbital altitude of 705 kilometers (438 miles), through a series of six ascent burns, the final one on June 17, 2002. The spacecraft is positioned in a near-polar orbit around the Earth in synchronization with the Sun, with its path over the ground ascending across the equator at the same local time every day, approximately 1:30 p.m. Correspondingly, on the other side of its orbit, Aqua descends across the equator at approximately 1:30 a.m. The early afternoon observation time contrasts with the 10:30-10:45 a.m. equatorial crossing time (descending in this case) of the EOS Terra satellite, launched in December 1999. The two daytime crossing times account for why the Terra and Aqua satellites were originally named "EOS AM" and "EOS PM," respectively. The combination of morning and afternoon observations will allow studies concerning the diurnal variability of many of the parameters discussed above.

More information on EOS and the science related to it can be found at the EOS Project Science Office website at http://eospso.gsfc.nasa.gov and at the Earth Observatory website at http://earthobservatory.nasa.gov. Further information on Aqua can be found at http://aqua.nasa.gov and at http://aqua.gsfc.nasa.gov.

next: Aqua Animations
back: Aqua Goals

 

pullquote

Aqua

Introduction
Aqua Goals
Mission Facts
Aqua Animations

Aqua First Light Images


  Aqua
Animations

Aqua Launch
Aqua was launched at 2:55 a.m. PDT on May 4, 2002 on board a Boeing Delta II 7920-10L launch vehicle from Vandenberg Air Force Base, California. This animation [48 MB QuickTime] shows the area surrounding the launch pad, the countdown, the rocket lift-off, and the spacecraft separation from the Delta rocket. (Animation by Reto Stockli)

  Aqua launch sequence

Solar Panel and Instrument Deployments
Shortly after achieving orbit, Aqua deployed its solar array, x-band antenna, and instruments. This time-accelerated sequence [20.1 MB QuickTime] shows the following deployments: solar array, AMSR-E antenna, CERES aft, CERES fore, X-Band antenna, MODIS Earth shield, and AIRS Earth shield. (Animation by Reto Stockli)

Aqua deploy sequence

Instrument Sensing
This animation [87 MB QuickTime] shows schematically the sensing of Aqua's six Earth-observing instruments, in the following order: CERES, AIRS, AMSU, HSB, MODIS, and AMSR-E. (Animation by Jesse Allen)

Aqua instrument sensing

Aqua Orbit
Aqua is positioned in a near-polar orbit around the Earth at an altitude of 705 km in synchronization with the Sun, with its path over the ground ascending across the equator at the same local time every day, approximately 1:30 p.m. Correspondingly, on the other side of its orbit, Aqua descends across the equator at approximately 1:30 a.m. [36.2 MB QuickTime] (Animation by Jesse Allen)

Aqua orbit

Aqua and Terra Orbits
Aqua's early afternoon observation time complements the 10:30-10:45 a.m. equatorial crossing time (descending in this case) of the EOS Terra satellite, launched in December 1999. The two daytime crossing times account for why the Terra and Aqua satellites were originally named "EOS AM" and "EOS PM," respectively. The combination of morning and afternoon observations will allow studies concerning the diurnal variability of the many parameters measured by both satellites. [34 MB QuickTime] (Animation by Jesse Allen)

Aqua and Terra Orbits

Afternoon Constellation
Because NASA has plans to launch a substantial number of Earth-observing spacecraft over the next 15 years, it would be more efficient to operate these spacecraft in groups, as opposed to single entities. In particular, the science output from the Aqua mission will be enhanced through coordinated flying with several other satellites that will be obtaining complementary data sets. These other satellites, in order after Aqua in the lead, are CALIPSO, CloudSat, PARASOL, and Aura. Because this sequence starts with Aqua and ends with Aura, it has been termed the "A-Train." [55.1 MB] (Animation by Jesse Allen)

Afternoon constellation

Atmospheric Infrared Sounder (AIRS)
The AIRS on Aqua is the first AIRS instrument and a major advance over earlier sounders flown in space. AIRS will measure atmospheric temperatures, humidities, and a host of other products, in order to improve weather forecasting and the understanding of climate processes. This artist's concept animation [18 MB QuickTime] shows the AIRS instrument measuring air temperatures at five levels in the atmosphere, each level indicated by a separate color. (Animation by Jesse Allen)

AIRS Scanning Swath

Advanced Microwave Sounding Unit (AMSU)
On Aqua, AMSU is integrally coupled with the AIRS instrument. Since 1998, AMSU instruments have also flown on satellites of the National Oceanic and Atmospheric Administration. This artist's concept animation [12 MB QuickTime] shows the AMSU instrument measuring air temperatures at five levels in the atmosphere, each level indicated by a separate color. (Animation by Jesse Allen)

AMSU Scanning Swath

Humidity Sounder for Brazil (HSB)
On Aqua, it is particularly important to obtain humidities under overcast conditions. This artist's concept animation [17 MB QuickTime] shows the HSB instrument measuring humidities at four levels in the atmosphere, each level indicated by a separate color. (Animation by Jesse Allen)

HSB Scanning Swath

Clouds and the Earth's Radiant Energy System (CERES)
There are two CERES on Aqua, following two on the Terra satellite, launched in 1999, and one on the Tropical Rainfall Measuring Mission, launched in 1997. This artist's concept animation [16.6 MB QuickTime] shows the CERES instruments (one in cross-track scan mode, the other in biaxial scan mode) measuring heat emitted (outgoing longwave radiation) to space from the Earth's surface. (Animation by Jesse Allen)

CERES Scanning Swath

Moderate Resolution Imaging Spectroradiometer (MODIS)
The Aqua MODIS is the second MODIS, the first having been launched in 1999 on board the Terra satellite. This artist's concept animation [19.9 MB QuickTime] shows the MODIS instrument measuring clouds, land surface cover, snow cover on the land, and sea ice cover on the oceans. (Animation by Jesse Allen)

MODIS Scanning Swath

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