Aqua (satellite)

The name "Aqua" comes from the Latin word for water. The satellite was launched from Vandenberg Air Force Base on May 4, 2002, aboard a Delta II rocket. Aqua operated in a Sun-synchronous orbit as the third in the satellite formation called the "A Train" with several other satellites (OCO-2, the Japanese GCOM W1, PARASOL, CALIPSO, CloudSat, and Aura) for most of its first 20 years; but in January 2022 Aqua left the A-Train (as Cloud Sat, CALIPSO and PARASOL had already done) when, due to its fuel limitations, it transitioned to a free-drift mode, wherein its equatorial crossing time is slowly drifting to later times, from its tightly controlled orbit.

Mission

Aqua is one of NASA's missions for Earth science operating in the A-Train constellation. It has demonstrated a very high level of precision in making the primary long-term measurements of the mission. These highly calibrated climate quality measurements of radiance, reflectance, and backscatter have been used to cross-calibrate past and present sensors launched by NASA, as well as a variety of sensors launched from other agencies and the international community. Thousands of scientists and operational users from around the world have made use of the Aqua data to address NASA's 6 interdisciplinary Earth science focus areas: Atmospheric Composition, Weather, Carbon Cycle and Ecosystems, Water and Energy Cycle, Climate Variability and Change, and Earth Surface and Interior.

Aqua has experienced some minor, non-mission ending anomalies.

Because of a 2007 anomaly with the Solid State Recorder (SSR) it can only hold two orbits worth of data.

A series of solar array and array regulator electronics anomalies starting in 2010 has led to the loss of 23 strings of solar cells out of a total of 132 strings by 2022 and another 10 were lost on ARE-1A on August 29, 2024.

A 2005 short circuit within a battery cell led to a partial loss of cell capacity.

On September 8, 2007, the Dual Thruster Module (DTM-2) Heater experienced an anomaly.

In 2009, a solar panel thermistor failed and an error in the Solar Array offset was detected. The offset issue has been corrected periodically since then.

On August 16, 2020, The Formatter Multiplexer Unit (FMU) experienced an anomaly, corrupting some data in the SSR and stopping all data streams until it was recovered on September 2, 2020. On February 22, 2022 the FMU/SSR suffered a sub-module failure from which it recovered on March 23, 2022.

A few days later in 2022, a single event upset while in the South Atlantic Anomaly resulted in a switch from Power Controller-A to B and an entry to Earth Point Mode. A full recovery was completed on April 15, 2022.

Aqua completed the last of its drag makeup maneuvers, mandated by fuel limitations, in December 2021 and the next month it entered a free-drift mode, slowly descending below the A-Train and drifting to later equatorial crossing times, and lower altitudes. It exceeded its desired mean local time in February of 2023. For a time Aqua was a candidate for a life-extending re-fueling mission, but that was never attempted. In August 2025, the end of mission plan was to shut down instruments on August 26, 2026, perigee lowering maneuvers in September and October and begin passivation of the spacecraft in November, though a January 2025 analysis determined there was a 96.9% probability that the spacecraft could function through the end of 2026. By June 2026, they were predicting it would operate into September.

In 2019, the worst-case scenario would result in a re-entry by 2046.