Launch evidence guides
Geostationary vs. Polar-Orbiting Satellites for Launch Observation
Published (UTC)
Which satellite had a useful chance to observe a launch? Start with the location and time, then check the instrument, scan footprint and actual files. Orbit type helps explain the opportunity, but it cannot tell you whether a particular launch was visible.
A geostationary imager can return to the same region repeatedly. A polar-orbiting imager can provide a different view and finer spatial sampling during an overpass. For a short-lived launch signature, those advantages answer different questions. A frequent scan is useful only if it covers the event; a detailed image is useful only if it was acquired at a relevant time.
One launch seen from two geostationary positions
On March 1, 2022, an Atlas V carried NOAA's GOES-T satellite from Cape Canaveral. NOAA published side-by-side GeoColor views from GOES-16 and GOES-17 showing the launch from the eastern and western observing positions. The two perspectives are a concrete reminder that an event can be observed from more than one geometry.
This is a published viewing example, not a thermal-detection benchmark. GeoColor is a display product, and NOAA's example does not measure the probability that either satellite would detect another launch. Nor does it establish that a polar-orbiting sensor was present or absent at that time.
The satellite names in an old example also matter. As checked on October 3, 2026, NOAA identifies GOES-19 as GOES East and GOES-18 as GOES West. GOES-16 and GOES-17 are now backups. Preserve the spacecraft identity that belongs to an observation rather than replacing it with the current occupant of the same operational role.
Compare instruments and products
The comparison below focuses on ABI on the GOES-R series and VIIRS on Suomi NPP and the JPSS satellites. It is not a specification for every geostationary or polar-orbiting mission. NASA describes VIIRS instruments on Suomi NPP, NOAA-20 and NOAA-21 in its MODIS-to-VIIRS transition guidance; check the relevant mission and product status for the date being studied.
| Question | GOES ABI | VIIRS |
|---|---|---|
| How is the scene revisited? | Repeated scans of a visible Earth disk and selected sectors from a near-fixed viewpoint. | Successive swaths collected as the spacecraft moves along its orbit. A useful overpass must coincide with the region and time. |
| What timing should I expect? | In Mode 6: full disk every 10 minutes, CONUS or PACUS every 5 minutes, and two mesoscale domains every 60 seconds or one every 30 seconds. | NASA Level-1B granules normally package 6 minutes of observations. That duration is not a 6-minute revisit of a location. |
| What spatial sampling is relevant? | ABI thermal infrared bands have nominal 2 km sampling at the satellite subpoint. Other bands have different sampling. | Image bands have nominal 375 m sampling at nadir; moderate-resolution bands have nominal 750 m sampling. Band choice still matters. |
| What coverage must I verify? | The actual disk or sector, viewing angle and valid data at the event. The GOES pair does not provide global coverage. | The actual swath footprint, valid pixels and acquisition time. Global observation capability over time is not continuous coverage of every site. |
| What can it contribute? | A sequence useful for comparing change before, during and after an event when available. | A complementary spatial and spectral observation when an overpass overlaps the event or its aftermath. |
Instrument values and scan modes come from NOAA's ABI channel and scan summary, NASA's VIIRS comparison and the NASA VNP02IMG product description. Sampling figures describe nominal instrument geometry; they are not guaranteed launch-location accuracy or minimum detectable object sizes.
Find the observation window before choosing the best image
Begin with a UTC event interval and a documented area of interest. Include enough time before and after the event to inspect the background and any continuing features. Keep the basis for that interval: a scheduled time, an operator's report and an image acquisition time are different kinds of evidence.
For ABI, identify which scan sector actually covered the location. The fastest mesoscale option does not apply to the whole disk, and those smaller domains can move. A general statement that ABI can scan every 30 seconds is not evidence that 30-second imagery exists for your launch.
For VIIRS, search the swath archive for the event interval and inspect the geolocation information. A satellite passing nearby is insufficient if the area falls outside the usable swath. Likewise, a later overpass may be useful for a persistent cloud or surrounding scene while saying little about a brief powered-flight signature. The archive search, rather than an orbit label, should determine which opportunity existed.
For both instruments, save file identifiers and acquisition start and end times. A scene is built over an interval. If scan-level or pixel-level time is available and the research question needs it, retain it instead of treating the entire image as one instantaneous photograph. Record unresolved timing precision explicitly.
Check usable data rather than nominal coverage
An archive hit is the start of inspection. Determine whether the relevant pixels are valid, whether clouds obstruct the feature of interest, and whether the viewing geometry makes a location comparison meaningful. The NASA VIIRS Level-1B user guide documents pixel and scan flags for conditions including missing data, calibration problems, saturation and bow-tie deletion. Apply the definitions for the product and collection actually used.
A map tile that looks sharp after zooming is not evidence of finer native measurement. Preserve the native grid and the resampling method when making a comparison. If two sensors use different bands, times or viewing angles, those differences remain even after their images have been placed on the same map.
The practical output is a small opportunity inventory: one row per candidate file, with spacecraft, instrument, product, band, time interval, footprint, quality status and the question it can address. Use separate outcomes for no matching file found, matching but unusable data and usable data with no identified signature. None, by itself, proves that no launch occurred.
Use complementary evidence without filling the gaps
A good analysis may use ABI to establish a sequence and VIIRS to add an overpass view. It may also have only one useful instrument. Do not turn an unavailable comparison into an assumed missed detection, or an attractive animation into proof of uninterrupted coverage.
For the separate question of what a thermal value means, read What a Satellite Thermal Signal Says About a Launch. This article's first job is to establish that an appropriate observation opportunity existed.
Then inspect LaunchDetect's USSF-385 public evidence record, which separates observed imagery from modeled paths and areas. This is a government mission and a separate example from GOES-T. The public API guide explains how to retrieve published summaries and link back to records; those summaries do not supply raw sensor files or prove the completeness of satellite coverage. Keep the observation inventory beside the interpretation so a reader can see what was available and what remains unknown.
Sources and further reading
Source pages checked October 3, 2026. Historical documents retain their stated version and event dates.
- NOAA current geostationary missions [N001]
- NOAA ABI scan modes and channel summary [N002]
- NOAA GOES East and West observe GOES-T launch, March 2022 [N003]
- NASA MODIS to VIIRS transition [N004]
- NASA VNP02IMG product and collection metadata [N005]
- NASA VIIRS L1B User Guide, August 2021, version 3 [N007]
- LaunchDetect existing thermal-signal explainer [LD001]
- LaunchDetect public detection API guide [LD002]
- LaunchDetect USSF-385 public evidence record [LD003]