Orbiting Carbon Observatory

Orbiting Carbon Observatory

Artist rendition of the OCO satellite as it would look in orbit
Mission type	Climatology
Operator	NASA
Mission duration	Launch failure Planned: 2 years
Spacecraft properties
Bus	LEOStar-2
Manufacturer	Orbital Sciences[1]
Launch mass	530 kg (1,170 lb)[1]
Payload mass	150 kg (330 lb)[1]
Dimensions	Stowed: 2.3 × 1.4 m (7.5 × 4.6 ft)[1]
Power	786 W[1]
Start of mission
Launch date	24 February 2009, 09:20 UTC
Rocket	Taurus-XL 3110
Launch site	Vandenberg LC-576E
Contractor	Orbital
Orbital parameters
Reference system	Geocentric
Regime	Sun-synchronous

The Orbiting Carbon Observatory (OCO) is a NASA satellite mission intended to provide global space-based observations of atmospheric carbon dioxide (CO₂). The original spacecraft was lost in a launch failure on 24 February 2009, when the payload fairing of the Taurus rocket which was carrying it failed to separate during ascent.^[2] The added mass of the fairing prevented the satellite from reaching orbit.^[3] It subsequently re-entered the atmosphere and crashed into the Indian Ocean near Antarctica.^[4][5] The replacement satellite, Orbiting Carbon Observatory 2, was launched 2 July 2014 aboard a Delta II rocket.^[6][7] The Orbiting Carbon Observatory 3, a stand-alone payload built from the spare OCO-2 flight instrument, will be installed on the International Space Station's Kibō Exposed Facility in December 2016.^[8]

Mission description

OCO's measurements are designed to be accurate enough to show for the first time the geographic distribution of carbon dioxide sources and sinks on a regional scale.^[9] The data is planned to improve the understanding of the global carbon cycle, the natural processes and human activities that influence the abundance and distribution of the greenhouse gas. This improved understanding is expected to enable more reliable forecasts of future changes in the abundance and distribution of carbon dioxide in the atmosphere and the effect that these changes may have on Earth's climate.

The A-Train satellite constellation

The OCO spacecraft was provided by Orbital Sciences Corporation.^[10] During its two-year mission, OCO will fly in a near polar orbit which enables the instrument to observe most of Earth's surface at least once every sixteen days. It is intended to fly in loose formation with a series of other Earth-orbiting satellites known as the Earth Observing System Afternoon Constellation, or the A-train. This coordinated flight formation was intended to enable researchers to correlate OCO data with data acquired by other instruments on other spacecraft. In particular, Earth scientists would like to compare OCO data with nearly simultaneous measurements acquired by the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite and ground-based data from the Total Carbon Column Observing Network (TCCON). Alignment with the A-train demands a particularly short launch window of 30 seconds.^[11]

The original cost of the mission was US$280 million.^[12] It was sponsored by NASA's Earth System Science Pathfinder Program.^[13] NASA's Jet Propulsion Laboratory in Pasadena, California, manages OCO for NASA's Science Mission Directorate.

Technology

The satellite will carry a single instrument designed to take the most precise measurements of atmospheric carbon dioxide ever made from space. The instrument consists of three parallel, high-resolution spectrometers, integrated into a common structure and fed by a common telescope. The spectrometers will make simultaneous measurements of the carbon dioxide and molecular oxygen absorption of sunlight reflected off the same location on Earth's surface when viewed in the near-infrared part of the electromagnetic spectrum, invisible to the human eye.

As sunlight passes through Earth's atmosphere and is reflected from Earth's surface, molecules of atmospheric gases absorb very specific colors of light. If the light is divided into a rainbow of colors, called a spectrum, the specific colors absorbed by each gas appear as dark lines. Different gases absorb different colors, so the pattern of absorption lines provides a telltale spectral "fingerprint" for that molecule. OCO's spectrometers were designed to detect these molecular fingerprints.

Each of the three spectrometers was tuned to measure the absorption in a specific range of colors. Each of these ranges includes dozens of dark absorption lines produced by either carbon dioxide or molecular oxygen. The amount of light absorbed in each spectral line increases with the number of molecules along the optical path. OCO's spectrometers measure the fraction of the light absorbed in each of these lines with very high precision. This information was then to be analyzed to determine the number of molecules along the path between the top of the atmosphere and the surface.

If the amount of carbon dioxide varies from place to place, the amount of absorption will also vary. To resolve these variations, the observatory's instrument will record an image of the spectrum produced by each spectrometer three times every second as the satellite flies over the surface at more than four miles per second. This information would then be transmitted to the ground, where carbon dioxide concentrations would be retrieved in four separate footprints for each image collected. These spatially varying carbon dioxide concentration estimates would then be analyzed using global transport models, like those used for weather prediction, to infer the locations of carbon dioxide sources and sinks.^[14]

The OCO instrument was developed by Hamilton Sundstrand Sensor Systems in Pomona, California, and the Jet Propulsion Laboratory.^[15]

Original launch

Launch of OCO's Taurus XL rocket

The satellite was originally launched from Vandenberg Air Force Base in California on a dedicated Taurus XL rocket. However, the payload fairing — a clam shell-shaped covering that protects the satellite during launch — apparently failed to separate from the spacecraft. "We have not had a successful launch tonight and will not be able to have a successful OCO mission," NASA commentator George Diller said.^[16]

Source: NASA^[17]

• Date: 24 February 2009, 1:55 a.m. PST
• Launch Vehicle: Orbital Sciences Taurus XL
• Launch Site: Vandenberg Air Force Base – Launch Pad SLC 576-E

The OCO launch failed because the Taurus-XL launcher payload fairing failed to separate. A payload fairing is a clamshell-shaped cover that encloses and protects a payload on the pad and during early flight. Fairings are a standard component of expendable launch vehicles, and they are always jettisoned as soon as possible after a rocket has climbed high enough for heating from air friction to no longer risk damaging the payload. On this flight, the fairing should have been jettisoned several seconds after Stage 2 ignition. The extra mass of the fairing was not a significant factor during the flight of the larger lower stages, but it kept the relatively small Stage 3 from adding enough velocity to reach orbit, so the resulting sub-orbital ballistic path took the payload into the ocean near Antarctica, 17 minutes after liftoff.^[18]

On 17 July 2009 NASA released a summary of its Mishap Investigation Board report.^[19] In the report the board provided recommendations to prevent any future problems associated with the four hardware components that could have caused the failure.

Reflight

Flight plan of OCO-2

Three days after the failed February 2009 launch, the OCO science team sent NASA headquarters a proposal to build and launch an OCO copy by late 2011.^[20] On 1 February 2010, the FY 2011 NASA budget request did include US$170 million for NASA to develop and fly a replacement for the Orbiting Carbon Observatory: OCO-2.^[21]

NASA, in 2010, initially selected Orbital Sciences for launching the replacement in February 2013 on a Taurus XL 3110 from Vandenberg Air Force Base in California.^[22] However, in February 2012 both NASA and Orbital Sciences came to an agreement to terminate the launch contract.^[23]

OCO-2 was initially scheduled for launch on 1 July 2014 at 2:56am PDT aboard a Delta II rocket, though that launch was scrubbed at 46 seconds on the countdown clock, due to a faulty valve on the water suppression system that is used to flow water on the launch pad to dampen the acoustic energy during launch. The rocket launched 2 July at the same time.^[24]

See also

• Greenhouse Gases Observing Satellite

References

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

1. 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.
2. "OCO Blog".
3. CO2 satellite crashes after lift-off
4. "NASA Satellite Crashes Back to Earth". News.nationalgeographic.com. Retrieved 28 February 2009.
5. Achenbach, Joel; Eilperin, Juliet (25 February 2009). "Satellite Crashes After Its Launch". washingtonpost.com. Retrieved 28 February 2009.
6. "Homepage: Orbiting Carbon Observatory-2 (OCO-2)". NASA. Jet Propulsion Laboratory. 2013. Retrieved 5 April 2014.
7. "NASA's OCO-2 brings sharp focus on global carbon". Phys Org. 3 April 2014. Retrieved 5 April 2014.
8. "OCO-3". NASA. Retrieved 1 June 2015.
9. "The NASA Orbiting Carbon Observatory (OCO) Mission: Objectives, Approach, and Status".
10. "Orbital Sciences Program Page".
11. Rosalie Murphy (27 June 2014). "Five Things About OCO-2". NASA. Retrieved 2 July 2014. The observatory has just a 30-second opportunity to launch. The timing has to be so precise because OCO-2 will join the A-Train, a constellation of five other international Earth observing satellites that fly very close together to make nearly simultaneous measurements of our planet. Launching a few seconds too early or late will prevent it from joining the right orbit track.
12. Amos, Jonathan (24 February 2009). "Failure hits Nasa's 'CO2 hunter'". BBC News. Retrieved 24 February 2009.
13. "NASA Earth System Science Pathfinder Program".
14. "Orbiting Carbon Observatory Science Writers' Guide" (PDF).
15. "OCO: Observatory". JPL.NASA.gov. Retrieved 26 February 2009.
16. NASA global warming satellite has troubled launch
17. "NASA's Shuttle and Rocket Missions Launch Schedule".
18. "NASA satellite crashes minutes after launch". CNN.com. 24 February 2009. Retrieved 28 February 2009.
19. "NASA Releases Orbiting Carbon Observatory Accident Summary". NASA. 17 July 2009.
20. Clark, Stephen (20 March 2009). "Orbiting Carbon Observatory team proposes replacement". Spaceflight Now. Retrieved 19 November 2009.
21. "The Federal Budget, Fiscal Year 2011: National Aeronautics and Space Administration". The White House. 1 February 2010. Archived from the original on 4 February 2010.
22. "NASA Awards Launch Services Contract for OCO-2 Mission" (Press release). NASA via PR Newswire. 22 June 2010. Retrieved 11 February 2012.
23. Clark, Stephen (10 February 2012). "Carbon-sniffing satellite faces one-year delay". Spaceflight Now. Retrieved 11 February 2012.
24. "Homepage: Orbiting Carbon Observatory-2 (OCO-2)". NASA. Jet Propulsion Laboratory. 2013. Retrieved 5 April 2014.

External links

• NASA/JPL Orbiting Carbon Observatory website
• JPL Science Division OCO page
• UStream video on OCO mission