As part of the Apollo-Soyuz Test Project (ASTP), Apollo was tracked in the satellite-to-satellite tracking mode by the NASA synchronous satellite ATS-F. The tracking data obtained at occultation of Apollo by the earth has been used in this study to compute atmospheric parameters like pressure and temperature. The results of the numerical inversion have been compared with data from a radiosonde station near the occultation site. Although this comparison lacks exact space-time coincidence because of the paucity of the data, it is of interest to report that near the surface of the earth, the refractivity computed from occultation data agreed with the radiosonde-derived values to within 3 percent. A pressure profile deduced from the refractivity profile by using a simplified model of the atmosphere showed good agreement with radiosonde measurements. Although the present results are based on one occultation pass and lack statistical validity, they demonstrate the feasibility of determining absolute pressure levels in the atmosphere from occultation measurements.