Save the ESPA login credentials as global environment to be used in other functions in rLandsat. This is a pre-requisite for running any of the other functions requiring espa-api
Usage
espa_creds(username, password)
Arguments
username
espa account's username
password
espa account's password corresponding to the username
Value
NULL. Just saves the username and password in .Reviron
Details
If you do not have an account with espa, please create one here: https://ers.cr.usgs.gov/register