  <li><span style="font-family: ms sans serif;">A function -
sfdj70 - to retrieve the observed, mean and geomagnetic activity of a
given date according to Jacchia's 70 model.<br>
          </span></li>
        <li><span style="font-family: ms sans serif;">A function -
sfdj77 - to retrieve the observed, mean and geomagnetic activity of a
given date according to Jacchia's 77 model.</span></li>
        <li><span style="font-family: ms sans serif;">A function - gst
- to calculate the Greenwich sidereal 