Orbiting Carbon Observatory 2
Artist depiction of OCO-2
|Mission duration||Planned: 2 years
Elapsed: 1 year, 4 months and 26 days
|Launch mass||454 kg (1,001 lb)|
|Dry mass||409 kg (902 lb)|
|Payload mass||131 kg (289 lb)|
|Dimensions||Stowed: 2.12 × 0.94 m (6.96 × 3.08 ft)|
|Start of mission|
|Launch date||2 July 2014, 09:56UTC|
|Rocket||Delta II 7320-10C|
|Launch site||Vandenberg SLC-2W|
|Contractor||United Launch Alliance|
|Semi-major axis||7,080.44 km (4,399.58 mi)|
|Perigee||701.42 km (435.84 mi)|
|Apogee||703.19 km (436.94 mi)|
|Argument of perigee||76.42°|
|Velocity||7.5 km/s (4.7 mi/s)|
|Epoch||15 May 2015, 19:41:10 UTC|
|Type||Near-IR Cassegrain (ƒ/1.8)|
|3 grated spectrometers|
Orbiting Carbon Observatory 2 (OCO-2) is an American environmental science satellite which launched on 2 July 2014. A NASA mission, it is a replacement for the Orbiting Carbon Observatory which was lost in a launch failure in 2009.
The OCO-2 satellite was built by Orbital Sciences Corporation, based around the LEOStar-2 bus. The spacecraft is being used to study carbon dioxide concentrations and distributions in the atmosphere.
OCO-2 was ordered after the original OCO spacecraft failed to achieve orbit. During the first satellite's launch atop a Taurus-XL in February 2009, the payload fairing failed to separate from around the spacecraft and the rocket did not have sufficient power to enter orbit with its additional mass. Although a Taurus launch was initially contracted for the reflight, the launch contract was cancelled after the same malfunction occurred on the launch of the Glory satellite two years later.
United Launch Alliance launched OCO-2 using a Delta II rocket at the beginning of a 30-second launch window at 09:56:23 UTC (2:56:23 PDT) on 2 July 2014. Flying in the 7320-10C configuration, the rocket launched from Space Launch Complex 2W at Vandenberg Air Force Base. The initial launch attempt on 1 July at 09:56:44 UTC was scrubbed at 46 seconds on the countdown clock due to a faulty valve on the water suppression system, used to flow water on the launch pad to dampen the acoustic energy during launch.
OCO-2 joined the A-train satellite constellation, becoming the sixth satellite in the group. Members of the A-train fly very close together in sun-synchronous orbit, to make nearly simultaneous measurements of Earth. A particularly short launch window of 30 seconds was necessary to achieve a proper position in the train. As of 15 May 2015 it was in an orbit with a perigee of 701.4 kilometres (435.8 mi), an apogee of 703.2 kilometres (436.9 mi) and 98.19 degrees inclination.
Column CO2 measurements
OCO-2 makes measurements in three different spectral bands over four to eight different footprints of approximately 1.29 km × 2.25 km (0.80 mi × 1.40 mi) each. About 24 soundings are collected per second while in sunlight and over 10% of these are sufficiently cloud free for further analysis. One spectral band is used for column measurements of oxygen (A-band 0.765 microns), and two are used for column measurements of carbon dioxide (weak band 1.61 microns, strong band 2.06 microns).
In the retrieval algorithm measurements from the three bands are combined to yield column-averaged dry-air mole fractions of carbon dioxide. Because these are dry-air mole fractions, these measurements do not change with water content or surface pressure. Because the molecular oxygen content of the atmosphere ( ie. excluding the oxygen in water vapour ) is well known to be 20.95%, oxygen is used as a measure of the total dry air column. To ensure these measurements are traceable to the World Meteorological Organization, OCO-2 measurements are carefully compared with measurements by the Total Carbon Column Observing Network (TCCON).
- "Orbiting Carbon Observatory-2 Launch" (PDF). NASA. July 2014. Retrieved 16 May 2015.
- Peat, Chris (15 May 2015). "OCO 2 - Orbit". Heavens-Above. Retrieved 16 May 2015.
- Osterman 2015, p. 7.
- Krebs, Gunter. "OCO 1, 2 (ESSP 5)". Gunter's Space Page. It has a mass of 454 kilograms (1,001 lb) and a design life of two years.
- "Carbon dioxide-sniffing spacecraft set to launch". Spaceflight Now. 28 June 2014. Retrieved 1 July 2014.
- Graham, William (30 June 2014). "ULA Delta II launch with OCO-2 rescheduled for Wednesday". NASASpaceflight.com. Retrieved 1 July 2014.
- "Delta II OCO-2 Mission" (PDF). United Launch Alliance. Retrieved 1 July 2014.
- "Launch of NASA's Orbiting Carbon Observatory-2 Rescheduled for July 2". NASA. 1 July 2014. Retrieved 1 July 2014.
- Rosalie Murphy (27 June 2014). "Five Things About OCO-2". NASA. Retrieved 2 July 2014.
- Parkinson, Claire L.; Ward, Alan; King, Michael D., eds. (2006). "Orbiting Carbon Observatory" (PDF). Earth Science Reference Handbook. NASA. pp. 199–203. Retrieved 14 May 2015.
- Osterman 2015, p. 5.
- Osterman, Gregory; et al. (30 March 2015). "Orbiting Carbon Observatory–2 (OCO-2): Data Product User's Guide, Operational L1 and L2 Data Versions 6 and 6R" (PDF). NASA. OCO D-55208. Retrieved 14 May 2015.
Media related to Orbiting Carbon Observatory-2 at Wikimedia Commons
- Orbiting Carbon Observatory at NASA.gov
- Orbiting Carbon Observatory by the Jet Propulsion Laboratory
- Orbiting Carbon Observatory by the JPL Science Division