SatPaths API (beta)

Technical information

SatPaths API calculates predictive schedules for flyovers over Australia and ground footprints for selected sensors (in most common mode of acquisition) on board the following non-commercial, public-good, mid to low resolution orbiting satellites operated by USGS, NASA, NOAA and ESA.

   AQUA (MODIS): 2,330km swath

   TERRA (MODIS): 2,350km swath

   NOAA 15 (AVHRR): 2,940km swath

   NOAA 18 (AVHRR): 2,940km swath

   NOAA 19 (AVHRR): 2,940km swath

   NOAA 20 (VIIRS): 2,940km swath

   NPP (VIIRS): 3,040km swath

   LANDSAT 7 (ETM+): 185km swath

   LANDSAT 8 (OLI): 185km swath

   LANDSAT 9 (OLI): 185km swath

   SENTINEL 1A (C-SAR): 250km – Interferometric Wide Swath Mode

   SENTINEL 1B (C-SAR): 250km – Interferometric Wide Swath Mode

   SENTINEL 2A (MSI): 290km swath

   SENTINEL 2B (MSI): 290km swath

   SENTINEL 3A (SLSTR): 1,270km swath

   SENTINEL 3B (SLSTR): 1.270km swath

   METOP-A (AVHRR): 2,900km swath

   METOP-B (AVHRR) : 2,900km swath

   METOP-C (AVHRR) : 2,900km swath

Predictive schedules are calculated for seven Australian ground stations which are participating in the ANGSTT network:

   Alice Springs (ALS), operated by Geoscience Australia

   Cleveland Bay (CFQ), operated by AIMS

   Cribb Point (CPT), operated by Australian Bureau of Meteorology

   Hobart (HBT), operated by CSIRO

   Learmonth (LMO), operated by Australian Bureau of Meteorology

   Murdoch (MUR), operated by Landgate

   Shoal Bay (DAR), operated by Australian Bureau of Meteorology

The timing and footprints of satellite overpasses are calculated based on the parameters specified in a two-line element set (TLE) from space-track.org. 

Accuracy and limitations

Flyover schedules are only indicative of potential acquisitions and will differ from what is actually downlinked from satellites by each ground station:

• The timings and footprints are relevant for a selection of ground stations in the ANGSTT network (i.e. operating on the Australian continent only). Some ground stations are omitted, such as those operating in Antarctica.
• Satellite overpass timings and footprints are accurate only up to a few days into the future. The information should be used with caution for dates exceeding the current date by more than 10 days. However, calculations for dates in the past are accurate since they are based on the most relevant historical input parameters.
• 'Start' and 'end' times indicate the earliest and latest time a particular satellite is visible from ground stations in the ANGSTT network.
• A satellite may be visible from a particular ground station, but it does not mean the station is used for, or is capable of, transferring the data acquired by that satellite, e.g. no data from the Sentinel constellation of satellites is downloaded by the ANGSTT network of ground stations.
• Calculated 'start' and 'end' times may not precisely reflect actual acquisition schedules of individual ground stations in the ANGSTT network. The differences could be due to:
  1. stations not having the capability of downlinking the data from a particular satellite
  2. stations not having the capacity to downlink data from multiple satellites at the same time (hence only higher priority satellites are scheduled for downlink to a particular station)
  3. ground station operators adjusting the acquisition time to accommodate satellites passing in quick succession and/or to limit data acquisition over the open ocean
  4. for various operational purposes, operators specifying different parameters to those used as input into calculations in this app
• Accuracy of time-at-location calculations is generally to within a minute of actual data acquisition time for the specified location.

Quality assurance

Validation of calculated predictive schedules and ground footprints was based on sample of actual acquisition schedules published by Alice Springs, Murdoch and Hobart ground stations, and actual imagery acquired by Geoscience Australia for the purpose of generation of DEA Hotspots .

See Accuracy and Limitations section above for more limitations.

Software

SatPaths API is written in Python. Calculations are based on the PyPredict library.