Is there an API to access live (or semi-live?) data from NOAA satellites, such as the GOES-R series? I've been searching for weeks, and I know there are ways to manually access data through website file systems, but I'm looking for something more like, for example, the NASA Mars Rover Photos API, or even just a data stream.
Where are you searching? The NOAA and all of its child departments/organizations provide a plethora of satellite and API datasets, including satellite datasets accessible via API. The list below is a tiny sampling of all three; I cannot stress enough how much more data there is. NOAA is basically a cornucopia of satellite/API datasets.
API Web Service - weather.gov
Web Services API (version 2) Documentation | Climate Data Online (CDO) | National Climatic Data Center (NCDC)
NCEI Data Service API User Documentation
Tides & Currents Web Services
Advanced Data Access Methods | National Centers for Environmental Information (NCEI) formerly known as National Climatic Data Center (NCDC)
NCDC Satellite Data
NCEI Satellite Data Services
NCEI Satellite Oceanography Group
NCDC's ArcGIS REST Services Directory
From my similar experience in a weeks-long search for an alternative to NOAA's CLASS archive, the answer is apparently no, or not yet. And AWS only has images, not other relevant variables of interest e.g. aerosol optical depth values.
That said, here's GOES-R decoder instructions.
The GOES-R decoder supports the ingest and display of NOAAport provisional products (currently on the NOTHER feed), as well as Level 2b netCDF files. A GOES-R Geostationary Lightning Mapper (GLM) decoder is also provided to handle sensor lightning observations.