Orbiting Carbon Observatory 2

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Orbiting Carbon Observatory 2
Orbiting Carbon Observatory-2 artist rendering (PIA18374).jpg
Artist depiction of OCO-2
Mission type Climatology
Operator NASA
COSPAR ID 2014-035A
SATCAT № 40059
Website oco.jpl.nasa.gov
Mission duration Planned: 2 years
Elapsed: 2 years, 1 month and 27 days
Spacecraft properties
Bus LEOStar-2
Manufacturer Orbital Sciences[1]
Launch mass 454 kg (1,001 lb)[1]
Dry mass 409 kg (902 lb)
Payload mass 131 kg (289 lb)[1]
Dimensions Stowed: 2.12 × 0.94 m (6.96 × 3.08 ft)[1]
Power 815 W[1]
Start of mission
Launch date 2 July 2014, 09:56 (2014-07-02UTC09:56Z) UTC
Rocket Delta II 7320-10C
Launch site Vandenberg SLC-2W
Contractor United Launch Alliance
Orbital parameters
Reference system Geocentric
Regime Sun-synchronous
Semi-major axis 7,080.44 km (4,399.58 mi)
Eccentricity 0.000125
Perigee 701.42 km (435.84 mi)
Apogee 703.19 km (436.94 mi)
Inclination 98.19°
Period 98.82°
RAAN 77.38°
Argument of perigee 76.42°
Mean anomaly 283.72°
Mean motion 14.57°
Velocity 7.5 km/s (4.7 mi/s)
Epoch 15 May 2015, 19:41:10 UTC[2]
Revolution number 4623
Main telescope
Type Near-IR Cassegrain (ƒ/1.8)[3]
Wavelengths 2.06 microns
1.61 microns
0.765 microns[1]
3 grated spectrometers
Orbiting Carbon Observatory-2 Logo.jpg

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. As an example of a proposed global fleet of monitoring satellites to verify or cast doubt on emission reports from the 196 member states of the United Nations Framework Convention on Climate Change, OCO-2 is expected to be in service till 2020.[4]

Mission description[edit]

The OCO-2 satellite was built by Orbital Sciences Corporation, based around the LEOStar-2 bus.[5] The spacecraft is being used to study carbon dioxide concentrations and distributions in the atmosphere.[6]

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.[7]

Launch of OCO-2 on a Delta II rocket.

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.[8] 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.[9]

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.[10] 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.[2]

Column CO2 measurements[edit]

Mollweide projected animation of CO2 data from the OCO-2 mission.

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.[11][12] 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).[3]

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 ( i.e. 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).[3]


  1. ^ a b c d e f "Orbiting Carbon Observatory-2 Launch" (PDF). NASA. July 2014. Retrieved 16 May 2015. 
  2. ^ a b Peat, Chris (15 May 2015). "OCO 2 - Orbit". Heavens-Above. Retrieved 16 May 2015. 
  3. ^ a b c Osterman 2015, p. 7.
  4. ^ Broad, William J. (May 9, 2016). "Potential Eyes in the Sky on Greenhouse Gases". NYT. Retrieved August 24, 2016. 
  5. ^ 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.
  6. ^ "Carbon dioxide-sniffing spacecraft set to launch". Spaceflight Now. 28 June 2014. Retrieved 1 July 2014. 
  7. ^ Graham, William (30 June 2014). "ULA Delta II launch with OCO-2 rescheduled for Wednesday". NASASpaceflight.com. Retrieved 1 July 2014. 
  8. ^ "Delta II OCO-2 Mission" (PDF). United Launch Alliance. Retrieved 1 July 2014. 
  9. ^ "Launch of NASA's Orbiting Carbon Observatory-2 Rescheduled for July 2". NASA. 1 July 2014. Retrieved 1 July 2014. 
  10. ^ Rosalie Murphy (27 June 2014). "Five Things About OCO-2". NASA. Retrieved 2 July 2014. 
  11. ^ 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. 
  12. ^ Osterman 2015, p. 5.


External links[edit]

Media related to Orbiting Carbon Observatory-2 at Wikimedia Commons