Outer radiation belt and solar proton observations with Explorer VII during March-April 1960

Introduction. The IGY composite satellite Explorer VII (1959ι ), launched on October 13, 1959, includes an instrument prepared by this laboratory Ludwig and Whelpley, 1960 for a 1-year comprehensive study of (a) the lower parts of the inner and outer radiation belts, (b) the primary cosmic-ray intensity near the earth, and (c) the arrival of solar protons/Table 1 summarizes the properties of the two Geiger tube detectors in this instrument. As of April 1, 1960, the orbit of Explorer VII was characterized by the following : perigee altitude 565 km, apogee altitude 1096 km, inclination 50.5°, anomalistic period 101.3 minutes. Typically, about five passes per day, each giving some 5 to 20 minutes of substantially continuous data, are received at the Iowa City station. The track of the satellite during the most favorable one of each day's passes is from northern California, across northwestern United States, southern Canada (nearly to the southern tip of Hudson Bay), and Newfoundland, terminating in mid-Atlantic. In the study of the effects at high magnetic latitude, observations during such portions of the orbit are the most valuable of any obtained with the present satellite. The next most advantageous portions are those south of Australia. All the data of the present report were derived from receptions at Iowa City and at the NASA stations at Blossom Point, Maryland, and Woomera, Australia. The positional coordinates of the satellite are determined by the NASA tracking chain and the Space Computing Center of the Goddard Space Flight Laboratory. We are indebted to that agency for the prompt receipt of the tabular ephemeris at 1-minute intervals of time. The present note is concerned with the period from the latter part of March to mid-April 1960. It is being published in advance of a more comprehensive survey because of the geophysical events of special interest during the period mentioned and because of the valuable support of the related and simultaneous observations with Pioneer V, which was in the near astronomical vicinity of the earth but well beyond its magnetic influence during this period (radial distance of 0.036 astronomical unit, approximately toward the sun, on April 1).