Aura (satellite)
Aura (EOS CH-1) is a multi-national NASA scientific research satellite in orbit around the Earth, studying the Earth's ozone layer, air quality and climate. It is the third major component of the Earth Observing System (EOS) following on Terra (launched 1999) and Aqua (launched 2002). Aura follows on from the Upper Atmosphere Research Satellite (UARS). Aura is a joint mission between NASA, the Netherlands, Finland, and the U.K.[2] The Aura spacecraft is healthy and is expected to operate until at least 2022, likely beyond.[3]
 Aura (EOS CH-1) | |
| Mission type | Earth Observation |
|---|---|
| Operator | NASA |
| COSPAR ID | 2004-026A |
| SATCAT no. | 28376 |
| Website | aura.gsfc.nasa.gov |
| Spacecraft properties | |
| Bus | T330 (AB-1200) |
| Manufacturer | Northrop Grumman |
| Launch mass | 2,970 kilograms (6,550 lb) |
| Dimensions | 4.70 m x 17.37 m x 6.91 m |
| Power | 4.6 kW |
| Start of mission | |
| Launch date | July 15, 2004, 10:01:51 UTC |
| Rocket | Delta II 7920-10L |
| Launch site | Vandenberg SLC-2W |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Sun-synchronous |
| Semi-major axis | 7,080.7 kilometers (4,399.7 mi) |
| Eccentricity | 0.0001111[1] |
| Perigee altitude | 708 kilometers (440 mi)[1] |
| Apogee altitude | 710 kilometers (440 mi)[1] |
| Inclination | 98.22 degrees[1] |
| Period | 98.83 minutes[1] |
| RAAN | 96.8126 degrees |
| Argument of perigee | 89.5089 degrees |
| Mean anomaly | 270.6277 degrees |
| Mean motion | 14.57112850 |
| Epoch | 25 January 2015, 03:15:27 UTC[1] |
The name "Aura" comes from the Latin word for air. The satellite was launched from Vandenberg Air Force Base on July 15, 2004, aboard a Delta II 7920-10L rocket.
The Aura spacecraft has a mass of about 1,765 kg (3,891 lb). The body is 6.9 m (23 ft) long with the extended single solar panel about 15 m (49 ft) long.
Aura flies in a sun-synchronous orbit, in formation with 6 other satellites, collectively known as the "A Train"; it is last in the formation. The other satellites in the formation are:
All satellites have an equatorial crossing time at about 1:30 in the afternoon, thus the name 'A (Afternoon) Train'.
Mission
As of 2015, there had been 1589 Aura-related journal articles. The scientific findings of these studies address key NASA research objectives related to stratospheric composition, air quality, and climate change.[3]
Aura has suffered some minor, non-mission ending anomalies.
On January 12, 2005, a solar array connector partially "unzipped" losing temperature telemetry and power from part of the solar array. On March 12, 2010, Aura lost power from one-half of one of the 11 solar panels and this was attributed to a Micrometeroid Orbital Debris (MMOD) strike. These events, and 8 other anomalies in the array regulation electronics (ARE), have resulted in an estimated loss of 28 out of 132 solar strings. Nonetheless the mission is estimated to have ample power capabilities to supply the mission until fuel runs out.[4][5][6]
A Formatter Multiplexer Unit (FMU) / Solid State Recorder (SSR) anomaly was first detected in December 2007. New symptoms were detected in January 2017 and starting on March 21, 2017, Aura no longer recorded housekeeping data to partition 31.[4]
In December of 2016, reaction wheel #3 spun down. It was recovered 10 days later.[4]
On January 31, 2018, the TES instrument was decommissioned due to degrading operations. A mechanical arm on the instrument began stalling intermittently in 2010, affecting TES's ability to collect data continuously. Despite the adaptations of TES operators, the degradation got worse with time and in 2017 the instrument lost operations for approximately half the year. It will continue to receive enough power to keep it from getting too cold which could affect the two remaining functioning instruments.[7]
As of 2017, the expected Constellation Exit and Decommissioning date is February 2023. An extended mission could push decommissioning back to February 2025, although it could be extended as far as 2036. Predicted re-entry would be 2044.[5]
Instruments
Aura carries four instruments for studies of atmospheric chemistry:
- HIRDLS — High Resolution Dynamics Limb Sounder — measures infrared radiation from ozone, water vapor, CFCs, methane and nitrogen compounds. Developed jointly with the United Kingdom Natural Environment Research Council. HIRDLS capabilities were compromised at launch when a piece of Kapton film in the instrument came loose and blocked much of the aperture, allowing only a partial view. The blockage prevented certain types of observations and necessitated the development of algorithms to remove the effects due to the blockage. This unanticipated algorithm developmental effort delayed data delivery. The HIRDLS chopper motor stalled on March 17, 2008, and HIRDLS has not produced science since.[8]
- MLS — Microwave Limb Sounder — measures emissions from ozone, chlorine and other trace gases, and helps to clarify the role of water vapor in global warming. The MLS instrument package is divided into the THz, GHz, and spectrometer modules. The THz module was developed to measure the OH radical in the stratosphere and mesosphere using heterodyne detection of thermal emission. These modules observe emissions across 20 bands. In February 2006, band 13, the primary MLS band for measuring HCl, began to exhibit symptoms of aging and was deactivated to conserve life. It now only makes periodic observations. On August 6, 2013, band 12, which measures N2O, shut down.[9][4]
- OMI — Ozone Monitoring Instrument — uses ultraviolet and visible radiation to produce daily high-resolution maps. Developed by the Finnish Meteorological Institute and the Netherlands Agency for Aerospace Programmes. In 2007, OMI began to experience a "row anomaly" which affected the quality of the radiance data. The row anomaly has continued to progress since then, with periods of stability.[10]
- TES — Tropospheric Emission Spectrometer — measures tropospheric ozone in infrared wavelengths, also carbon monoxide, methane and nitrogen oxides. TES's laser A, which is used for retrieving interferometer control, began operating below peak in 2007 but was resurrected to replace laser B which ceased operation in August 2016. Laser A now operates at only 10% power. In 2011, TES observations were shifted from global survey mode, in which it made continuous observations, to special operations mode, wherein it makes high sample density observations over specific targets. Furthermore, the TES Interferometer Control System (ICS) motor began stalling in 2015. Each stall takes days or weeks to recover from and as of 2017 there had been 15 of them.[3][4][11]
References
- "AURA Satellite details 2004-026A NORAD 28376". N2YO. 25 January 2015. Retrieved 25 January 2015.
- "Earth Science Reference Handbook" (PDF). Retrieved 7 September 2018.
- Liu, Guosheng (22 June 2015). "NASA Earth Science Senior Review 2015" (PDF). Retrieved 17 October 2017. Cite journal requires
|journal=(help) - Fisher, Dominic (13 June 2017). "Mission Status at Aura Science Team MOWG Meeting" (PDF). Retrieved 13 December 2017. Cite journal requires
|journal=(help) - Fisher, Dominic. "Mission Status for Earth Science Constellation MOWG Meeting at KSC: EOS Aura" (PDF). Retrieved 5 April 2018.
- Fischer, Dominic (12 June 2018). "Mission Status for Earth Science Constellation MOWG Meeting @ Sioux Falls SD EOS Aura" (PDF). Retrieved 7 September 2018. Cite journal requires
|journal=(help) - Buis, Alan (13 February 2018). "Farewell to a Pioneering Pollution Sensor". Retrieved 5 April 2018.
- Schoeberl, M (2011). "Aura Senior Review" (PDF). Retrieved 17 October 2017. Cite journal requires
|journal=(help) - Livesey, Nathaniel J. "MLS Version 3.3 Level 2 data quality and description document" (PDF). Retrieved 13 December 2017.
- "Background information about the Row Anomaly in OMI". Retrieved 13 December 2017.
- Vandemark, Douglas. "NASA Earth Science Senior Review Subcommittee Report - 2017" (PDF). Retrieved 14 December 2017.