Aquarius (spacecraft)
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| Aquarius (spacecraft) | |
|---|---|
| Name | Aquarius |
| Mission type | Earth observation |
| Operator | NASA / CONAE |
| COSPAR ID | 2011-040A |
| SATCAT | 37752 |
| Mission duration | Planned: 3 years, Final: 5 years, 10 months, 19 days |
| Spacecraft bus | SAC-D |
| Manufacturer | INVAP / Goddard Space Flight Center |
| Launch mass | 1,350 kilograms (2,980 lb) |
| Launch date | June 10, 2011, 14:20:13 UTC |
| Launch rocket | Delta II 7320-10C |
| Launch site | Vandenberg Space Force Base SLC-2W |
| Decay date | June 7, 2015 (terminated), June 19, 2015 (re-entry) |
| Orbit reference | Geocentric orbit |
| Orbit regime | Sun-synchronous orbit |
| Orbit periapsis | 657 kilometers (408 mi) |
| Orbit apoapsis | 670 kilometers (420 mi) |
| Orbit inclination | 98.0 degrees |
| Orbit period | 98.0 minutes |
| Apsis | gee |
Aquarius (spacecraft). The Aquarius/SAC-D observatory was a major international Earth science mission dedicated to measuring global sea surface salinity. A joint venture between NASA and Argentina's CONAE, the spacecraft's primary instrument was the Aquarius radiometer-scatterometer, designed to provide the first space-based, global maps of salt concentration in the ocean's top layer. The mission aimed to improve understanding of the water cycle, ocean circulation, and climate by mapping salinity with unprecedented accuracy over its planned three-year lifetime.
Overview
The Aquarius mission was a cornerstone of collaborative Earth observation between NASA and the CONAE. It was the primary payload on the SAC-D satellite bus, built by the Argentine firm INVAP. Operating in a Sun-synchronous orbit, the observatory provided consistent lighting conditions for its suite of instruments. The mission represented a significant technological leap, as measuring subtle salinity variations from space required extremely sensitive microwave instrumentation to detect the faint electromagnetic radiation emitted by the ocean's surface.
Development and launch
Development of the Aquarius instrument was led by NASA's Goddard Space Flight Center and the Jet Propulsion Laboratory, with the SAC-D platform provided by CONAE. International contributions included instruments from Italy, France, and Canada. After extensive testing, the integrated spacecraft was launched on June 10, 2011, aboard a United Launch Alliance Delta II rocket from Vandenberg Space Force Base in California. The launch vehicle successfully placed the observatory into its intended polar orbit, marking the beginning of commissioning activities for the sophisticated payload.
Mission and scientific objectives
The primary scientific objective was to trace the global water cycle by measuring sea surface salinity, a key tracer for understanding freshwater input from precipitation, river runoff, and ice melt, and freshwater loss through evaporation. By creating detailed monthly salinity maps, scientists sought to elucidate the ocean's role in climate variability, including phenomena like El Niño. Secondary objectives, supported by the satellite's other instruments, included monitoring sea ice, tracking wildfires, and studying atmospheric phenomena and space weather.
Instrumentation and design
The core instrument was the Aquarius L-band radiometer-scatterometer system, which combined three highly sensitive radiometers with a scatterometer to correct for ocean surface roughness caused by wind. The satellite bus, SAC-D, housed several complementary instruments: the Italian ROSA for atmospheric sounding, the Canadian NIRST for monitoring high-temperature events, a microwave radiometer, a camera system, and a technology demonstration package from France. The spacecraft's design emphasized precise thermal control and stability to ensure the accuracy of the delicate salinity measurements.
Data and findings
Aquarius returned the first global maps of ocean salinity from space, revealing vast, stable salty regions in the subtropics and fresher zones near the equator and poles. Its data significantly advanced the study of intense rainfall events, river plumes like those from the Amazon River, and the interactions between ocean salinity and phenomena such as hurricanes. The mission provided critical validation for climate models and improved the understanding of ocean-atmosphere interactions. Data was processed and distributed by NASA's Physical Oceanography Distributed Active Archive Center.
End of mission and legacy
The mission ended on June 7, 2015, following a spacecraft attitude control system failure that made it impossible to maintain the precise pointing required for data collection. The satellite underwent a controlled decommissioning and re-entered Earth's atmosphere over the South Pacific Ocean on June 19, 2015. Aquarius's legacy endures through its foundational, multi-year dataset, which remains essential for ongoing research into the global water cycle and climate change. Its success paved the way for subsequent salinity missions like the European Space Agency's SMOS and continues to inform oceanography and climate science.
Category:NASA spacecraft Category:Earth observation satellites Category:Spacecraft launched in 2011