Solar radio flux for orbit determination: nowcast and forecast

The project

Modelling the upper atmosphere density is essential for nowcasting and for predicting satellite orbits at low altitude (<1500 km). Density variations are primarily driven by solar activity, for which the 10.7 cm radio flux (the F10.7) is routinely used as a solar proxy. However, it has been demonstrated that the DTM-2013 (Drag Temperature Model [Bruinsma, 2015]) performs better with the 30 cm radio flux for altitudes lower than 500 km [Dudok de Wit et al., 2014].

The Nobeyama Radio Observatory performs daily measurements of the 30 cm radio flux on an operational 7/365 basis. Additional measurements are made at 15, 8.2, 3.0, and 1.8 cm. The radio polarimeters are operated by the Nobeyama Radio Observatory (NRO), a branch of National Astronomical Observatory of Japan (NAOJ).

As an operator of Low Earth Satellites and hence a user of density models, the French Space agency (CNES) has contracted CLS to lead a project in collaboration with the LPC2E aiming at nowcasting and predicting the level of radio flux at these different wavelengths.

Cnes - Centre National d'Etudes SpatialesLPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

The data

The links below point to two archives: daily radio fluxes at 3.2 cm, 8 cm, 15 cm and 30 cm measured since Nov. 1, 1957, and predictions for the next 30 days. Provisional values (up to 30 days old) are corrected for outliers. Data gaps are filled in by expectation-maximization, and flares are removed. The forecasts are based on a non-recursive analogue neural network.

Fluxes at the real Sun-Earth distance are referenced as “absolute”, and fluxes at 1 AU (Astronomical Unit) are referenced as “adjusted”.

Solar flux archive

Solar flux forecast


Radio Polarimeters at the Nobeyama Radio Observatory []

Dudok de Wit, S. Bruinsma, K. Shibasaki, Synoptic radio observations as proxies for upper atmosphere modelling, Space Weather and Space Climate 4 (2014) A06, doi:10.1051/swsc/2014003, [online]

Bruinsma, The DTM-2013 thermosphere model, Space Weather and Space Climate, 5 (2015), A1, doi: 10.1051/swsc/2015001, [online]