Atmosphere API update: automated retrieval of space weather indices
Satellites in Low Earth Orbit (LEO) occupy a region of Earth’s atmosphere known as the thermosphere. Even though the air is rarefied, it does result in drag forces on satellites and debris, affecting the decay of their orbits. Being able to predict the orbits of satellites and space debris is critical to safe space operations in an increasingly cluttered environment. In order to make those predictions, we need accurate models of thermospheric mass density.
The Committee on Space Research (COSPAR) is an international body that promotes scientific space research. The COSPAR International Reference Atmosphere 2012 recommends the use of two models to calculate themospheric density and composition:
- NRLMSISE00 —developed by the US Naval Research Laboratory.
- JB2008 — developed by Space Environment Technologies and the US Air Force Space Command.
Amentum’s Atmosphere API (accessible here) provides programmatic access to both. The nrlmsise00 and jb2008 API endpoints both calculate atmospheric density at a given altitude, latitude, longitude, date, and UTC time. The nrlmsise00 API endpoint previously required users to specify space weather indices, including:
- The average “ap” values in the 24 hours preceding the given date,
- F10.7 cm radio emissions for the previous day, and
- the 81 day average of the same centered on the given date.
In response to feedback from users, we have updated the Atmosphere API to automatically retrieve space weather indices from online data sources (the US National Oceanic and Atmospheric Administration for radio flux data and GFZ German Research Centre for Geosciences for ap indices). The calculated average values are also returned in the JSON response for reference.
Figure 1 above shows the updated API in action. The global map of thermospheric density is plotted at 3 hour timestamps during the geomagnetic storm of November 2018. The diurnal variation caused by solar heating of the atmosphere (varying with time, latitude, and longitude) is apparent. The geomagnetic storm peaked around the 5th day, leading to significant increases in density that affected the orbits of satellites and debris. Note that the surge in density is pronounced at higher latitudes — caused by coupling of the magnetosphere to the solar wind (also evidenced by increased auroral activity). An excellent scientific review of thermospheric mass density, and the physical phenomena affecting it, can be found here.
The updated Atmosphere API is live and ready to use. As always, we welcome and appreciate any feedback or questions that you have.
team@amentum.space
