There are a growing number of methane satellites either in orbit or on the drawing boards. Until now, they have fallen into one of two categories: global mapping and point-source.
Global mapping detectors are designed to identify and quantify broad emission patterns at a very wide scale. The European Space Agency’s TROPOMI instrument is a leading example. By contrast, point-source detectors, are built to measure relatively large methane emissions from specific predetermined point locations. A prime example is GHGSat.
MethaneSAT represents a new approach. It has a much wider field of view and much higher precision (meaning it’s more sensitive) than a point-source system, and a much lower detection threshold and higher spatial resolution compared to a global mapper.
Table 1: MethaneSAT vs. TROPOMI
|System Description Item||MethaneSAT||TROPOMI|
|Weight||350kg||900kg (Sentinel-5P satellite)|
|Swath (field of view)||200km||2600km|
|Pixel size (smallest element)||400m x 100m||7,000m x 7,000m|
|Planned number of satellites||1||1|
* Threshold at 1 km x 1 km pixel size.
Global vs. point-source instruments
Global mappers have a larger pixel size — the smallest viewable element — which gives more precise measurement than point-source detectors. Today’s global mappers like TROPOMI, which has a 7,000 meter pixel, can only detect very large individual point sources, on the order of several thousand kilograms or more per hour, or very large emitting area sources.
Point-source detectors have fine-grained spatial resolution with a pixel size in the tens of meters. They are designed to look at specific targets identified in advance, and which have relatively high emissions rates. For example, the new Iris satellite from GHGSat has a field of view of 12km with a relatively high detection threshold (the methane concentration enhancement detectable by the sensor), of ~50 parts per billion precision.
Point-source instruments are generally smaller and less expensive, making it possible to use a constellation of multiple satellites to provide frequent monitoring of pre-determined target sites and can be used to keep a close watch on specific locations with higher emission rates.
MethaneSAT combines key capabilities
MethaneSAT 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, allowing for quantification of almost all emissions and tracking changes in those emissions over time.
It combines key capabilities of both point-source and global mapping systems. It has a wide field of view coupled with very high precision sensors, enabling it to quantify emissions over areas with diverse types of emitters, whether small and diffuse sources or large and concentrated ones.
MethaneSAT will also detect high-emitting point sources, with less spatial granularity, compared to point-source detectors. But with its much broader swath, MethaneSAT will be able to revisit sites more frequently and cover a larger proportion of emission sources than a point-source satellite. This will enable MethaneSAT to capture a wide range of emissions, allowing for robust emission quantification encompassing both area- and point sources.
MethaneSAT is designed to be more precise than point-source systems, with its methane measurement precision at least 10 times more sensitive, at the same time providing a 20 times larger swath, than the GHGSat Iris instrument (Table 2 below). Due to the challenging technical demands to achieve its mission goals MethaneSAT is 10 times the size of GHGSat.
Table 2: MethaneSAT vs. GHGSat
|System Description Item||MethaneSAT||GHGSat|
|Swath (field of view)||200km||12km|
|Pixel size (smallest element)||400m x 100m||30m x 30m|
|Planned number of satellites||1||>10|
* Threshold at 1 km x 1 km pixel size.