How it fits into the methane measurement eco-system
How does MethaneSAT compare to other methane detection satellites? The answer is that these systems fall into three basic categories, depending on the kind of measurements they’re designed to take. To develop a full understanding of the methane emissions picture, it takes multiple measurement types.
At one end of the spectrum are global mapping detectors, ideal for measuring broad, long term trends at the regional or planetary scale; at the other end are point-source detection systems, designed to identify large methane emitters over relatively small areas.
In between are area-source detectors, like MethaneSAT. This newly emerging type of instrument has a much wider field of view than a point-source system, and a much lower detection threshold (meaning more sensitive) and higher spatial granularity (meaning it collects more detailed data at higher resolution) compared to a global mapper.
MethaneSAT is designed to augment and deepen the information we are beginning to get from other satellite systems, either orbiting now or in the planning stages.
We describe all three kinds of system in detail below and explain how they work together.
Methane detection system summary comparison
Global mapping detectors
Global mapping detectors are designed to measure large scale trends in methane concentrations across big regional areas with relatively high emissions. The TROPOMI instrument launched by the European Space Agency falls into this class.
Comparison between MethaneSAT and TROPOMI
|System Description Item||MethaneSAT||TROPOMI|
|Weight||350kg||900kg (Sentinel satellite)|
|Swath width (field of view)||260km||2600km|
|Detection threshold (ppb)||2ppb||12ppb|
|Pixel size (smallest element)||400m x 100m||7,000m x 7,000m|
|Planned number of satellites||1||1|
Both global and area-source detectors can be used to identify and quantify large point-source methane emissions. In the current state-of-the-art, however, global detectors (e.g. TROPOMI) can only detect very large point source emitters (i.e. several thousand kilograms methane per hour, if not more).
Although their larger pixel size means that global and area-source detectors offer more precise measurement than point-source detectors, global-detectors, in particular, tend to have much higher detection thresholds than point-source instruments.
Whereas point-source detectors tend to be compact compared with area-source systems TROPOMI is larger than the area-source system on MethaneSAT.
Point-source detectors are designed to look at very small areas, typically with high detection (less sensitive) thresholds. They are well suited for measuring emissions from known targets with relatively high emissions rates. For example, GHGSat has a field of view of 12km with a relatively high detection threshold (the methane concentration enhancement detectable by the sensor), of ~100 parts per billion (ppb) precision.
Point-source detectors also have fine spatial resolution with a pixel size – the smallest viewable element – in the tens of meters range. Point-source instruments are typically less expensive than the other types, making it more affordable to use a constellation of multiple satellites to provide frequent monitoring of pre-determined target sites. Alternatively, some of them are small enough to fit on an airplane.
GHG Sat and other point-source technologies are diagnostic tools that can zero in on specific facilities to pinpoint the exact location of a problem or a leak. They can be used to keep a close watch on a source that is known to a reoccurring problem.
Most of the methane detecting systems either operating now or known to be on the drawing board are point-source detectors. Along with GHGSat, the category also includes the system proposed by the State of California and Planet Labs; and the microsatellite system announced by Bluefield, (along with the AVIRIS-NG, which flies on a small aircraft operated by NASA’s Jet Propulsion Laboratory.
An area-source system like MethaneSAT combines key capabilities of both point-source and global mapping systems. They have a field of view of hundreds of kilometers wide, coupled with very high precision sensors, enabling them to quantify emissions over areas with diverse types of emitters (whether small and diffuse sources or large and concentrated ones).
An area-source detector can also detect high-emitting point sources, but with less spatial granularity, compared to point-source detectors. This capability enables area-source detectors to capture a wide range of emissions, allowing for robust emission quantification encompassing both area- and point sources.
Area-source detectors are designed to be more precise than point-source systems. For example, MethaneSAT has a detection threshold at least 10 times more sensitive than the current GHGSat satellite (Table 2 below). Due to the challenging science demands of high-precision area-source systems, they are typically larger as well. For example, MethaneSAT is 10 times bigger than GHGSat.
At present, MethaneSAT is the only known high-precision area-source detection system that fills a critical data and observing gap between point source and global mapping satellites. It is designed to augment and deepen the information we are beginning to get from point-source and global mapping missions.
Comparison between MethaneSAT and GHGSat
|System Description Item||MethaneSAT||GHGSat|
|Swath width (field of view)||260km||12km|
|Detection threshold (ppb)||2ppb||~100ppb|
|Pixel size (smallest element)||400m x 100m||30m x 30m|
|Planned number of satellites||1||>10|
Combining high-precision with broad path
High-precision area detection is important because a large proportion of overall methane emissions comes from sources that would fall below the detection threshold of the point-source instruments currently flying or proposed. Likewise, the ability to generate high-precision data measured across wide areas allows overall trends in methane emissions by sector to be monitored.
MethaneSAT will provide regular monitoring of regions accounting for more than 80 percent of global oil and gas production on a roughly weekly basis, with enough detail to identify both location and emission rates with an unprecedented degree of precision. Data analysis will then determine responsibility for those emissions, offering a valuable new metric for a wide range of stakeholders.
Without the capability to accurately measure overall emissions and understand their sources, comprehensive emission reduction efforts become much more difficult, because a large portion of emissions would be invisible, and thus unaccounted for. Similarly, area-source emissions are not well understood; at present there exist only snapshots provided by aircraft surveys, mostly representing just a few parts of North America.
Matrix of measurement satellites
MethaneSAT plays a unique and important role in the ecosystem of sensor types required to gather the data needed to know how best to reduce methane emissions.
For example, TROPOMI provides data about areas across the globe that have very large emissions. MethaneSAT will provide weekly data from many target regions around the world, quantifying almost all emissions and as well as larger point sources. This makes it possible to assess the full measure of the problem, determine who is responsible, and press for action.
Meanwhile, the California/Planet mission and GHGSat’s technology can be used by countries or companies to measure and monitor specific facilities with large emissions, for regulatory enforcement or operational compliance, once such measures are in place.