Daily SatPaths

Daily SatPaths

Data product

Version:

1.0.3-beta

Type:

Data service

Data updates:

Daily frequency, Ongoing

Provisional product

This is a provisional product, meaning it has not yet passed quality control and/or been finalised for release.

Overview

About

Geoscience Australia’s predictive schedules for public good satellites over Australia.

Access the data

For help accessing the data, see the Access tab.

Access the API

Get via API

Key specifications

For more specifications, see the Specifications tab.

Technical name	Daily Satellite Paths predictor
DOI	10.26186/146512
Tags	earth_observation, satellite, satellite_schedules
Licence	Creative Commons Attribution 4.0 International Licence

Cite this product

Data citation

Geoscience Australia, 2022. Geoscience Australia's predictive schedules for public good satellites over Australia. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/146512

Description

Background

Every day more than a dozen foreign-operated, public-good, non-commercial, medium to low resolution satellites fly over Australia and its territories. They cross the continent several times a day and their sensors capture images of the land and coastal waters.

Satellite overpass schedules for each spacecraft are predictable and can be calculated with a degree of accuracy. The Daily SatPaths provides information on which satellite sensors have and will potentially acquire data over Australia during a given date and time interval. It is important to note that actual acquisition schedules may differ from those presented in Daily SatPaths due the operational limitations of the satellite.

What this product offers

Daily SatPaths calculates date-specific predicted schedules for flyovers over Australia for 19 of the most popular public good satellites used by researchers in academia, and by public and private sector organisations.

The data can be displayed on an interactive map, the portion of Australia that is “visible” to those satellite sensors on each flyover (i.e. the so-called “ground footprint”).

The flight path schedules and sensor specific footprints can be downloaded in a tabular format (.csv file) and polygons in GeoJSON format for use in GIS software.

Applications

The information helps to answer three basic questions:

• What satellites are flying over Australia on a particular day, where and at what time?

• Which satellite sensors will potentially acquire data over an area of specific interest?

• Which ground stations in the Australian National Ground Segment Technical Team ANGSTT network those satellites are visible from, hence which of those stations could potentially downlink the data?

Technical information

Daily SatPaths 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:

• MODerate resolution Imaging Spectroradiometer (MODIS)

  • AQUA: 2,330km swath

  • TERRA: 2,350km swath

• Advanced Very High Resolution Radiometer (AVHRR)

  • NOAA 15: 2,940km swath

  • NOAA 18: 2,940km swath

  • NOAA 19: 2,940km swath

  • METOP-A: 2,900km swath

  • METOP-B: 2,900km swath

  • METOP-C: 2,900km swath

• Visible Infrared Imaging Radiometer Suite (VIIRS)

  • NOAA 20: 2,940km swath

  • Suomi NPP: 3,040km swath

• Landsat

  • Landsat 7 (ETM+): 185km swath

  • Landsat 8 (OLI): 185km swath

  • Landsat 9 (OLI): 185km swath

• Copernicus Programme

  • 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

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 Australian Institute of Marine Science

• 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. These parameters are updated once a day and are republished in a text file by Geoscience Australia as a free service.

Lineage

Information on start and end times for satellite flyovers, as well as position of satellites at a given time, are generated in real-time based on the most relevant two-line element set (TLE) data from spacetrack.org and jspredict library with algorithms ported from Predict open source tracking and orbital prediction software (https://www.qsl.net/kd2bd/predict.html).

Ground footprint information is generated based on published, sensor specific swath widths, using general purpose ellipsoidal geometry spatial libraries latlon-ellipsoidal.js and latlon-vincenty.js .

Software

Daily SatPaths single page application is written in HTML5 and JavaScript.

It uses third party data and open source libraries, including:

• TLE information from SpaceTrack.org

• ground station locations from angstt.gov.au

• base map by OpenStreetMap contributors

• jquery

• jquery UI

• leafletjs

• momentjs

• momentjs timezones

• satellite.js

• jspredit

• vector3djs

• latlon-ellipsoidal.js

• latlon-vincenty.js

• dms.js

• ResizeSensor.js

• ElementQueries.js

• dataTables.js

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

Quality

Accuracy

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. They do not reflect actual ground station reception schedules.

• Satellite overpass timings and footprints are accurate only within a few days of the current date. The information should be used with caution for dates lagging or exceeding the current date by more than 10 days.

• ‘Start’ and ‘end’ times indicate the earliest and latest time a particular satellite is visible from a given location. They are based on the location’s altitude and minimum angle the antenna can see over the horizon. That angle is set between 2 and 5 degrees for different stations to better reflect actual acquisition capabilities of each ground station.

• 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

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 .

Specifications

Product information

This metadata provides general information about the product.

Short name	Daily SatPaths	The name that is commonly used to refer to the product.
Technical name	Daily Satellite Paths predictor	The full technical name that refers to the product and its specific provider, sensors, and collection.
Version	1.0.3-beta	The version number of the product.
Lineage type	Data service	Our standard lineage types are ‘Baseline’ and ‘Derivative’.
Spatial type	None	The most common spatial types are raster and vector.
Update frequency	Daily	The expected frequency of data updates. Also called ‘Temporal resolution’.
Update activity	Ongoing	The activity status of data updates.
DOI	10.26186/146512	The Digital Object Identifier.
Licence	Creative Commons Attribution 4.0 International Licence	See the Credits tab.

Product categorisation

This metadata describes how the product relates to other DEA products.

Tags	earth_observation, satellite, satellite_schedules

Access

Access the data

Get via API

Access the API

Learn how to use the API

Use constraints

Information generated by the Daily SatPaths app is for general interest and educational purposes only. It should not be used in operational capacity. Geoscience Australia does not guarantee that the information is accurate, complete or free of errors.

Can I access the two-line element sets used to calculate Satpaths?

Yes!

These parameters are updated once a day and are republished in a text file by Geoscience Australia as a free service.

The original TLE sets are sourced from space-track.org.

History

Version history

No previous versions are available.

Credits

License and copyright

© Commonwealth of Australia (Geoscience Australia).

Released under Creative Commons Attribution 4.0 International Licence.