Orbiting Carbon Observatory 3

The Orbiting Carbon Observatory-3 (OCO-3) is a NASA-JPL instrument designed to measure carbon dioxide in Earth's atmosphere. The instrument is mounted on the Japanese Experiment Module-Exposed Facility on board the International Space Station (ISS).^[4] OCO-3 was scheduled to be transported to space by a SpaceX Dragon from a Falcon 9 rocket on 30 April 2019,^[5] but the launch was delayed to 3 May, due to problems with the space station's electrical power system.^[6] This launch was further delayed to 4 May due to electrical issues aboard Of Course I Still Love You (OCISLY), the barge used to recover the Falcon 9’s first stage.^[7] OCO-3 was launched as part of CRS-17 on 4 May 2019 at 06:48 UTC.^[8] The nominal mission lifetime is ten years.^[3]

Orbiting Carbon Observatory-3 (OCO-3)

The Japanese Experiment Module, EFU 3 is the occupied location second from the left.
Operator	NASA
Manufacturer	Jet Propulsion Laboratory[1]
Instrument type	Grating spectrometer
Function	Atmospheric CO2 and SIF
Mission duration	10 years (nominal) Elapsed: 5 years, 6 months
Website	www.jpl.nasa.gov/missions/orbiting-carbon-observatory-3-oco-3/
Properties
Mass	500 kg (1,100 lb)[2]
Dimensions	1.85 × 1.0 × 0.8 m (6.1 × 3.3 × 2.6 ft)
Power consumption	600 W
Resolution	Less than 4 km2 (1.5 sq mi)
Spectral band	2.06 microns 1.61 microns 0.765 microns[3]
Data rate	8 footprints, 3 Hz (24 per second)
Host spacecraft
Spacecraft	International Space Station
Launch date	4 May 2019, 06:48 UTC
Rocket	Falcon 9
Launch site	Cape Canaveral, SLC-40

OCO-3 was assembled using spare materials from the Orbiting Carbon Observatory-2 satellite.^[4] Because the OCO-3 instrument is similar to the OCO-2 instrument, it is expected to have similar performance with its measurements used to quantify CO₂ to 1 ppm precision or better at 3 Hz.^[9]

History and timeline

• 24 February 2009 - Orbiting Carbon Observatory was launched on a Taurus XL rocket but failed to achieve orbit when the fairing failed to separate from the satellite.^[10]
• 1 February 2010 - The 2010 President's budget included funding for development and re-flight of an OCO replacement.^[11]
• October 2010 - The Orbiting Carbon Observatory-2 project went into implementation phase.^[12]
• 2 July 2014 - OCO-2 was successfully launched from Vandenberg Air Force Base with a Delta II rocket.^[12]
• 2015 - Funding for the OCO-3 project cancelled.^[13]
• 22 December 2015 - OCO-3 project authorized to proceed. Funding was included in the 2016 spending bill.^[12][14]
• 16 March 2017 - OCO-3 was not included in the proposed FY2018 presidential budget.^[15]
• 23 March 2018 - Funding for the OCO-3 project was restored.^[16]
• May 2018 - Instrument underwent TVAC testing.^[17]
• 4 May 2019 - Launched using a Falcon 9 rocket from Cape Canaveral Air Force Station. The delivery was part of SpaceX CRS-17, which also included delivery of STP-H6 and a cargo resupply.^[18]
• After arrival - Robotic installation onto Exposed Facility Unit 3 (EFU 3) on the JEM-EF.^[19]

Instrument design

OCO-3 is constructed from spare equipment from the OCO-2 mission. Thus its physical characteristics are similar, but with some adaptations. A 2-axis pointing mirror was added, which will allow targeting of cities and other areas on order of 100 by 100 km (62 by 62 mi) for area mapping (also called "snapshot mode").^[3][17][19] A 100 m (330 ft) resolution context camera was also added.^[17] An onboard cryocooler will maintain detector temperatures of around −120 °C (−184 °F).^[20] Entrance optics were modified to maintain a similar ground footprint to OCO-2.^[3]

Similar to OCO and OCO-2, the main measurement will be of reflected near-IR sunlight. Grating spectrometers separate incoming light energy into different components of the electromagnetic spectrum (or wavelengths or "colors"). Because CO₂ and molecular oxygen absorb light at specific wavelengths, the signal or absorption levels at different wavelengths provide information on the amount of gases.^[20] Three bands are used called Weak CO₂ (around 1.6 μm), Strong CO₂ (around 2.0 μm), and Oxygen-A (around 0.76 μm).^[3] There are 1,016 spectral elements per band, and measurements are made simultaneously at 8 side-by-side locations or "footprints" each about 4 km² (1.5 sq mi) or smaller, 3 times per second.

Expected data use

Overall measurements from OCO-3 will help quantify sources and sinks of carbon dioxide from terrestrial ecosystems, the oceans, and from anthropogenic sources. Due to the ISS orbit, measurements will be made at latitudes less than 52°. Data from OCO-3 are expected to significantly improve understanding of global emissions from human activities, for example, using measurements over cities.^[9] Near simultaneous observations from other instruments onboard the International Space Station such as ECOSTRESS (measuring plant temperatures) and Global Ecosystem Dynamics Investigation lidar (measuring forest structure) may be combined with OCO-3 observations to help improve the understanding of the terrestrial ecosystem. Similar to OCO-2, OCO-3 will also measure Solar Induced Fluorescence which is a process that occurs during plant photosynthesis.^[3][21]

See also

• Greenhouse Gases Observing Satellite
• Space-based measurements of carbon dioxide
• Total Carbon Column Observing Network

References

1. "NASA.gov" (PDF). Archived from the original (PDF) on 2019-04-05. Retrieved 2019-04-05.
2. Eldering, Annmarie (2013). The OCO-3 Mission: An Overview (PDF). 9th International Workshop on Greenhouse Gas Measurements from Space. 29–31 May 2013. Yokohama, Japan.
3. Eldering, Annmarie; Taylor, Tommy E.; O'Dell, Chris W.; Pavlick, Ryan (2018). "The OCO-3 mission; measurement objectives and expected performance based on one year of simulated data". Atmospheric Measurement Techniques Discussions: 1–54. doi:10.5194/amt-2018-357.
4. "Mission to Earth: Orbiting Carbon Observatory 3". NASA/Jet Propulsion Laboratory. Retrieved February 16, 2019.
5. Sarah, Loff. "SpaceX CRS-17 Launch Now Scheduled for April 30". NASA. Retrieved April 19, 2019.
6. Derek Richardson (30 April 2019). "Space station power problem delays CRS-17 Dragon launch". spaceflightinsider.com. Retrieved 2 May 2019.
7. @SpaceX (3 May 2019). "Standing down today due to an electrical issue on the Of Course I Still Love You droneship. Teams will also address the ground side helium leak before tomorrow's backup launch opportunity at 06:48 UTC" (Tweet). Retrieved 6 May 2019 – via Twitter.
8. Potter, Sean (May 4, 2019). "SpaceX Dragon Heads to Space Station with NASA Science, Cargo". nasa.gov. NASA. Retrieved May 6, 2019.
9. Martin, David. "OCO-3 Quick Facts". NASA/Jet Propulsion Laboratory. Archived from the original on March 31, 2019. Retrieved February 16, 2019.
10. Bergin, Chris (February 24, 2009). "Orbital's Taurus XL fails during Orbiting Carbon Observatory spacecraft launch". NASASpaceFlight.com. Retrieved February 16, 2019.
11. Atkinson, Nancy (February 1, 2010). "NASA Budget Details: Constellation Cancelled, But Where To Next?". Universe Today. Retrieved February 16, 2019.
12. Martin, David. "OCO-3 History". NASA/Jet Propulsion Laboratory. Archived from the original on March 31, 2019. Retrieved February 16, 2019.
13. "OCO-3 Mission". NASA/Jet Propulsion Laboratory. Archived from the original on April 15, 2019. Retrieved April 23, 2019.
14. Werner, Debra (December 17, 2015). "NASA Reviving Effort To Put Spare Orbiting Carbon Observatory Sensor on ISS". Space News. Retrieved February 16, 2019.
15. "A grim budget day for U.S. science: analysis and reaction to Trump's plan". Science. March 16, 2017. Retrieved February 16, 2019.
16. Siegel, Ethan (March 23, 2018). "Winners And Losers In NASA's Budget For 2018 And Beyond". Forbes. Retrieved February 16, 2019.
17. Eldering, Annmarie (2018). The OCO-3 Mission: Science Objectives and Instrument Performance (PDF). 14th International Workshop on Greenhouse Gas Measurements from Space. 8–10 May 2018. Toronto, Ontario.
18. "May the 4th be with you: SpaceX CRS-17 Dragon launches to ISS". May 4, 2019. Retrieved May 5, 2019.
19. Crisp, David; et al. (September 9, 2018). "A Constellation Architecture for Monitoring Carbon Dioxide and Methane from Space" (PDF). Committee on Earth Observation Satellites. Retrieved February 16, 2019.
20. Martin, David. "OCO-3 Instrument". NASA/Jet Propulsion Laboratory. Retrieved February 16, 2019.
21. "PIA18935: Global Solar-Induced Fluorescence". NASA/Jet Propulsion Laboratory. December 18, 2014. Retrieved February 16, 2019.