April 2024

How Teledyne's Image Sensors Measure Greenhouse Gases

Measuring Greenhouse Gases from Space

To develop greenhouse gas mitigation strategies, it is important to not only know the average concentration of gases but to understand where the greenhouse gases are produced (“sources”) and where greenhouse gases are absorbed (“sinks”). A global view of greenhouse gases is most efficiently generated by space-based instruments flying in low Earth orbit (LEO). Teledyne is playing a key role in several space missions that are measuring greenhouse gas concentration, distribution, and sources and sinks. This article discusses the following space missions that use Teledyne’s light sensing focal plane arrays (FPAs):

NASA's Orbiting Carbon Observations -2 and -3	Operational
NASA's EMIT (Earth Surface Mineral Dust Source Investigation)	Operational
MethaneSat - funded by the Environmental Defense Fund	March 2024 Launch
Carbon Mapper - funded by philanthropic sources	Planned 2024 launch
ESA's CO2M	2025 launch

Orbiting Carbon Observatories

While scientists understand how CO₂ can affect temperature, they do not fully understand the geographic distribution of the sources and sinks of CO₂ and how the concentrations change over time. Enhancing this understanding is the mission of NASA’s two operational Orbiting Carbon Observatories: The Orbiting Carbon Observatory-2 (OCO-2) satellite, launched in 2014, operates in a polar orbit, as shown in the figure below. Orbiting Carbon Observatory-3 (OCO-3) was installed on the International Space Station in May 2019 and is collecting data that complements the OCO-2 data. (The original OCO was launched in 2009 but did not reach orbit due to failure of the launch vehicle fairing separation.)

The Orbiting Carbon Observatories determine carbon dioxide levels from space by measuring absorption of reflected sunlight in the near-infrared spectrum. OCO-2’s science instrument consists of three high-resolution spectrometers, integrated into a common structure and illuminated by a common telescope. The spectrometers make simultaneous measurements of the amount of reflected sunlight absorbed by CO₂ in the 1.61 and 2.06 μm bands. Those measurements are calibrated by measuring molecular oxygen (O₂) at 0.76 μm. These three bands are shown in the figure below.

Scientists use these data to determine the relative concentrations of CO₂ and O₂ in the sampled columns of Earth’s atmosphere. The ratio of measured CO₂ to O₂ is used to determine the concentration of atmospheric CO₂ to a precision of 0.3 to 0.5 percent (1 to 2 parts per million). The spectrometer optics produce a 2-dimensional image of the spectra on a 1024×1024 (18 µm pitch) pixel focal plane array (FPA). All three of the FPAs used by OCO-2 are Teledyne’s proven HAWAII-1RG detectors that have been used on several space missions. The focal plane array in the oxygen channel uses a silicon light detecting material, while the CO₂ channels use mercury cadmium telluride (HgCdTe) light detecting material with a 2.5 µm cutoff wavelength.

The Orbiting Carbon Observatories (OCO-2 and OCO-3) operate in low Earth orbit (LEO). These instruments achieve a spatial resolution of 1.3 km cross-track and 2.25 km along-track. The instruments only sense a 10.2 km wide swath of the ground during each 99 minute orbit. It takes 87 orbits of OCO-2, 16 days, to sample the full Earth and there is a gap of 16 days between measurements of any location.

EMIT (Earth Surface Mineral Dust Source Investigation)

In July 2022, a new generation of Earth observation instrument was installed on the International Space Station. Developed by NASA’s Jet Propulsion Laboratory, EMIT, the Earth Surface Mineral Dust Source Investigation, is measuring the mineral content of arid regions around the world. EMIT is a high fidelity imaging spectrometer that accurately measures the light reflected from the Earth at 286 wavelengths from the ultraviolet to the short-wave infrared (380 to 2500 nm; the human eye can see 400-700 nm). Since materials on the Earth have unique spectral “fingerprints”, the spectra can be used to produce mineral maps, maps of vegetation type and health, and sources of greenhouse gases. Examples of the spectra measured on six continents since the start of science on July 27, 2022 are shown below.

Since EMIT commenced science operations, the EMIT science team has identified more than 50 “super-emitters” of methane in Central Asia, the Middle East, and the southwestern United States. Methane’s spectral fingerprint and maps of three super-emitters are shown below.

NASA published two press releases on the EMIT spectrograph and science on October 25, 2022. The press releases can be found at:
https://www.nasa.gov/feature/jpl/nasa-dust-detective-delivers-first-maps-from-space-for-climate-science/
https://www.nasa.gov/feature/jpl/methane-super-emitters-mapped-by-nasa-s-new-earth-space-mission/

In 2023, JPL published an article on measurement of methane and carbon dioxide emission sources. In the article, detailed analyses of several human-produced carbon dioxide and methane super-emitters are analyzed; an example is shown below.

The article can be found at: https://www.science.org/doi/10.1126/sciadv.adh2391

Identifying anthropogenic sources of methane is very important to reduction of global warming of the Earth. While carbon dioxide is the dominant source of greenhouse gas effects, methane is a growing issue since methane emissions are increasing and over a 20-year period, methane is 80 times more effective than carbon dioxide for trapping the Earth’s heat. Methane has a much shorter “lifetime” in the Earth’s atmosphere than does carbon dioxide. Methane will persist for about a decade in the Earth’s atmosphere whereas carbon dioxide lingers for centuries. Elimination of sources of methane emissions will have a much faster effect than reduction of carbon dioxide.

JPL has developed and deployed several generations of imaging spectrometers and EMIT utilizes decades of technology advancements including a compact Dyson optical design (see below) that includes a high precision optical slit and diffraction grating, all designed and fabricated at JPL.

The detector for EMIT is produced by Teledyne Imaging Sensors (TIS) in Camarillo, California. TIS has worked with JPL since the 1990s to advance the performance of imaging arrays that simultaneously detect light from the ultraviolet through the shortwave infrared. The CHROMA-A image sensor used in EMIT has over 600,000 pixels and is mounted in a package that was optimized for the Dyson spectrometer design. A variable anti-reflection coating that is applied to the surface of the infrared detector is specifically tuned for the wavelengths that land on different regions of the detector.

Teledyne has a multi-decade partnership with JPL to provide visible-SWIR FPAs for imaging spectrometers used in seven space missions to the Moon, Mars, Jupiter’s moon Europa, and Earth observation. In addition, most of JPL’s airborne imaging spectrometers have used Teledyne’s sensors. General information on EMIT can be found at: https://earth.jpl.nasa.gov/emit/

MethaneSat

Most space missions that measure greenhouse gases are funded by NASA, the European Space Agency (ESA), or the national space agencies of Japan (JAXA), France (CNES), Germany (DLR), and Italy (ISA). However, the active and planned missions do not yet provide the global coverage required to find and accurately measure all sources of greenhouse gas emissions on a frequent basis. To help fill the gaps in measurement and spur mitigation actions, non-governmental organizations have started to sponsor greenhouse gas missions. MethaneSat is a mission being sponsored by the Environmental Defense Fund (EDF). In parallel, the non-profit Carbon Mapper has been established with philanthropic funds. Teledyne is supplying focal plane arrays to MethaneSat and Carbon Mapper; in this section we describe the MethaneSat mission. The following section presents Carbon Mapper.

MethaneSat’s objective is to provide data that will motivate reduction of methane emissions from the global oil and gas sector. The goal is to help reduce methane emissions from the oil and gas sector by 40% in 2025 and by 70% in 2030. MethaneSat will use two spectrometers to measure O₂ in the 1.249-1.305 µm band and measure CH₄ and O₂ in the 1.598-1.683 µm band. Typically, when designing a greenhouse gas measurement instrument, the instrument is optimized for one of two objectives:

1. Large area / high precision / poor spatial resolution
• This approach measures large areas of the Earth (several hundred km swath width) with low spatial resolution (1 to 10 km) but with high precision of gas concentration (0.25%). Results from these instruments can be used to guide narrower field of view instruments that focus on small-sized emission sources.
• Example missions are: OCO-2, OCO-3, CO2M (presented in the next section)
2. Small area / moderate precision / high spatial resolution
• This approach measures smaller areas due to its narrower field of view (30 to 80 km swath width) but has high spatial resolution to precisely locate “point source” emitters (pixel size of 30 to 60 meters).
• However, the finer spatial sampling reduces the amount of light that is collected during each frame of data as a LEO satellite flies over the Earth at 8 km/sec. Thus, these instruments provide lower precision of gas concentrations (1.2% to 6%).
• Example missions are: EMIT, Carbon Mapper

Both types of instruments are useful. The large area instrument can be used to provide high precision measurements of the emission from an entire country while the small area mappers can pinpoint and quantify small area super-emitters.

MethaneSat is attempting to combine the best of both approaches – achieving a relatively large swath width (200 km), good precision (0.24 – 0.5%), and relatively high spatial resolution (100×400 m²). MethaneSat uses two Teledyne GeoSnap-18 2048×2048 (2K×2K) HgCdTe focal plane arrays (FPAs) with a 1.8 µm cutoff. There is one GeoSnap-18 2K×2K FPA in each of the two spectrometers of MethaneSat. These FPAs were delivered to Ball Aerospace (now BAE Systems) which built the spectrometers.

MethaneSat was launched on March 4, 2024. Prior to launch, the project team has been flying a first version of the instrument, named MethaneAir, in a Lear jet at 40,000 feet to map the major oil and gas production regions in the United States (see map below)

For more information on MethaneSat, please visit: https://www.methanesat.org/

Carbon Mapper

Carbon Mapper, Inc. is a non-profit (501 c3) entity that has formed a coalition of private and public sector persons who have the combined expertise to deploy a science-driven service for maximum impact on government policies and mitigation efforts. The partners of Carbon Mapper are Planet, NASA’s Jet Propulsion Laboratory, the State of California, the University of Arizona, Arizona State University, the Rocky Mountain Institute, and philanthropic sponsors.

Carbon Mapper envisions a constellation of 16 satellites to provide rapid revisit time across the entire Earth. Funding has been raised for the first two satellites with the first planned for launch in 2024. Carbon Mapper engaged Planet to build the spectrometer instruments to measure CO₂ and CH₄. Designing and fabricating a high performance imaging spectrometer is a very specialized skill and Planet has taken the approach to learn from the expertise at the Jet Propulsion Laboratory (JPL). The first satellite will use a JPL designed and fabricated spectrometer, a process followed by Planet staff. For the second instrument, Planet will take the lead in instrument fabrication and assembly, with assistance from JPL. The first two Carbon Mapper instruments are similar to the NASA JPL EMIT instrument which uses a Teledyne CHROMA-A 1280×480 pixel (30 µm pitch) visible-SWIR FPA.

The animation below shows the orbit of two satellites in Phase 1 (tech demo) of Carbon Mapper, with the full constellation of 16 satellites in Phase 2 (if enough funding can be found).

CO2M

The Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) is a European Space Agency (ESA) mission that will measure carbon dioxide that is released into the atmosphere by human activity. CO2M is a low Earth orbit (LEO) wide field of view (500 km swath width) push-broom spectrometer that will measure CO₂ with a precision of 0.7 ppm and CH₄ with a precision of 10 ppb at a spatial resolution of 2×2 km. CO2M is planned to be a three satellite constellation with launch of the first satellite (CO2M-A) in 2025. The figure below is an artist concept of the CO2M satellite.

CO2M will be equipped with three instruments that work together to provide accurate measurement of CO₂:

• Integrated CO₂ and NO₂ Imaging Spectrometer (CO2I) that observes CO₂, CH₄, and NO₂ emissions
• A 3-band CLoud IMager (CLIM) that will detect clouds so that the effect of clouds can be removed in the analysis of the CO2I data.
• A Multi-angular Multi-band Polarimeter (MAP) that estimate aerosols to further improve the data analysis.

Teledyne’s CIS120 backside illuminated CMOS FPA is being used in all three instruments to sense light over 400 – 900 nm (0.4-0.9 µm) wavelengths. The CIS120, which has 2048×2048 (2K×2K) pixels with 10 µm pitch, is shown in the figure below. Two of the instruments (CO2I and CLIM) also incorporate infrared FPAs that are supplied by European companies.