Orbiting Carbon Observatory 2

Orbiting Carbon Observatory 2

Artist depiction of OCO-2
Mission type Climatology
Operator NASA
COSPAR ID 2014-035A
SATCAT № 40059
Website http://oco.jpl.nasa.gov/
Mission duration Planned: 2 years
Elapsed: 1 year and 9 months
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]
Instruments
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.

Mission description

The OCO-2 satellite was built by Orbital Sciences Corporation, based around the LEOStar-2 bus.[4] The spacecraft is being used to study carbon dioxide concentrations and distributions in the atmosphere.[5]

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.[6]

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.[7] 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.[8]

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.[9] 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

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.[10][11] 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]

References

  1. 1 2 3 4 5 6 "Orbiting Carbon Observatory-2 Launch" (PDF). NASA. July 2014. Retrieved 16 May 2015.
  2. 1 2 Peat, Chris (15 May 2015). "OCO 2 - Orbit". Heavens-Above. Retrieved 16 May 2015.
  3. 1 2 3 Osterman 2015, p. 7.
  4. ↑ 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.
  5. ↑ "Carbon dioxide-sniffing spacecraft set to launch". Spaceflight Now. 28 June 2014. Retrieved 1 July 2014.
  6. ↑ Graham, William (30 June 2014). "ULA Delta II launch with OCO-2 rescheduled for Wednesday". NASASpaceflight.com. Retrieved 1 July 2014.
  7. ↑ "Delta II OCO-2 Mission" (PDF). United Launch Alliance. Retrieved 1 July 2014.
  8. ↑ "Launch of NASA's Orbiting Carbon Observatory-2 Rescheduled for July 2". NASA. 1 July 2014. Retrieved 1 July 2014.
  9. ↑ Rosalie Murphy (27 June 2014). "Five Things About OCO-2". NASA. Retrieved 2 July 2014.
  10. ↑ 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.
  11. ↑ Osterman 2015, p. 5.

Bibliography

External links

Media related to Orbiting Carbon Observatory-2 at Wikimedia Commons

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