# GMAT atmosphere

I am using GMAT to propagate satellite motion with Jacchia-Roberts atmosphere model. Here is a formula used from this model which is then used to estimate the variation in drag on a spacecraft due to heating by solar activity:

$$T_c(K) = 379 + 3.24\cdot F_{10.7} + 1.3[F_{10.7} – \overline{F}_{10.7}]$$

in which $F_{10.7}$ and $\overline{F}_{10.7}$(the average daily solar flux at a 10.7 cm wavelength for the day of interest and 81-day running average of $F_{10.7}$ centered on the day of interest, respectively) are used.

I would like to ask; where does GMAT take this coefficients from and where can I find the $\overline{F}_{10.7}$ in order i would like to implement Jacchia-Roberts?

As it is seen from definition, a values not only before but also after this day will be needed to calculate $\overline{F}_{10.7}$ but I couldn't find a resource in the internet providing me such information.

Here is a NASA repository of space weather data, including f10.7.

https://omniweb.gsfc.nasa.gov/form/dx1.html

I would bet GMAT gets its data there or a similar site.

EDIT

Apologies everyone for the lacking answer, I'm new to StackExchange. That original link actually only has historical data, so it probably isn't the best source.

I found this old GMAT forum post (http://forums.gmatcentral.org/viewtopic.php?f=3&t=43555) that says GMAT gets solar weather data from CSSI/Celestrak: http://www.celestrak.com/spacedata/. This post is old, so I can't guarantee that's still what GMAT uses, but that's also the source my company uses for space weather data for operational OD so it's probably a safe bet anyways.

This has historical and a few months of daily predictive data you could use, including f10.7 and other common space weather indices. Hope this helps.

• it looks much better now! By the way if you make a change that addresses someone's comment, leave a short comment with the @ sign in front of their user name. That way they get a notification and will know that you've addressed the issue. In this case I just found this by accident. Looks much better now! – uhoh Aug 14 '18 at 15:53