Ion Densities in the Lower D-Region Measured with a Parachuted Probe

Abstract

A parachute-borne instrument package for performing measurements in the lower ionosphere between 80 and 40 km altitude has been developed by the ESTEC Space Science Department. The parachute probe is a piggy-back on Skylark rockets. It is ejected from the rocket during ascent at about 45 km height and braked by a drag parachute to an apogee of about 80 km. At this height an internal timer releases the drag parachute of 0.75 m diameter and the main parachute of 2.5 m diameter is deployed. The package descends to an altitude of 15 km where two thirds of the rigging lines are cut off by explosive bolts, triggered by a barometric switch. The package then falls rapidly to the ground, thus reducing the potential air traffic risk. A schematic view of the rocket and probe trajectories and of the sequence of events is shown in Figure 1.