SWIR imaging spectrometer vs thermal IR camera for methane detection
A thermal IR camera shows a heat contrast that a gas plume happens to disturb. A SWIR imaging spectrometer measures the actual absorption signature of methane against reflected sunlight. They're not competing on the same physics, and that's exactly why operators who've run both end up using them for different jobs.
How each sensor actually sees methane
A thermal IR camera, the kind used for handheld OGI surveys, works by detecting a difference in infrared radiance between the gas and the background. Methane absorbs in a narrow band around 7.7 microns, and the camera renders that absorption as a visible "smoke" on the screen. It's a contrast measurement. No contrast, no plume on screen, even if gas is actually there.
A SWIR imaging spectrometer works differently. It collects hundreds of narrow spectral bands across the shortwave infrared, typically 1,000 to 2,500 nanometers, and fits the measured spectrum against methane's known absorption features at 1.65 and 2.3 microns. This is a quantitative measurement of how much light got absorbed on its way down to the ground and back up to the sensor, not a visual heat difference. That's the basis of column enhancement retrievals, the ppm-m numbers you see in plume reports.
Where thermal IR camera limits show up in daily MRV work
Thermal cameras need thermal contrast between the plume and whatever's behind it. Calm, uniform-temperature conditions, which happen a lot at dawn and dusk, flatten that contrast and the plume goes invisible even though emissions haven't changed. Wind is the other problem: above roughly 10 mph, plumes disperse faster than a handheld or truck-mounted thermal survey can walk the fence line, so crews either miss the window or have to come back.
Thermal IR is also fundamentally a presence/absence tool at the pad level. It tells a crew that a component is leaking, which is exactly what it's built for. It doesn't give you a quantified rate, and it doesn't scale past the sites a crew can physically drive to in a quarter. For an MRV analyst trying to reconcile a basin-level regional advisory against operated sites, a once-a-quarter site walk can't tell you what happened on the days nobody was standing at the fence.
Why shortwave infrared methane sensing holds up better at scale
Shortwave infrared methane sensing from a satellite platform doesn't depend on thermal contrast at all. It depends on daylight and a reasonably bright ground surface, which describes most well pads and tank batteries. That means it keeps working in the still-air, low-wind-shear conditions that blind thermal cameras, and it works from altitude, which is what lets a single pass attribute a plume to a site boundary instead of a county.
The tradeoff runs the other way too. SWIR needs sunlight, so it's a daytime-only method, and retrieval quality depends on surface albedo, cloud cover, and tasking availability over your acreage. It won't replace a handheld OGI survey for pinpointing which valve on a skid is leaking. What it's good for is the question that keeps coming up in MRV reconciliation: is this specific site emitting today, or is the regional bulletin pointing at someone else's pad in the same basin.
That's the gap a per-site plume map built on imaging spectrometry is built to close, resolving the SWIR absorption signature down to a site boundary on a daily cadence where tasking allows, instead of waiting on an annual flyover or a coarse regional advisory to name a facility.
If you're reconciling basin-level advisories against your own operated sites, it's worth seeing what a per-site view looks like for your acreage.