Abstract: Retarding potential analyzers (RPAs) have been used for decades on orbital spacecraft. The RPA described in this thesis is known as the Dartmouth Petite Ion Probe (PIP) and has been developed for use on suborbital sounding rockets. The PIP is configured to make measurements of the ion populations present in ionospheric plasma. Past science flights employing the PIP have been concerned with nightside phenomena. Measurement goals of upcoming flights have necessitated modifications to the PIP to enable dayside functionality. When the PIP is exposed to sunlight a photocurrent is observed that contaminates the signal from the intended plasma measurement. The work described here is focused on the addition of a screen to suppress photoelectrons as well as testing and modeling of the performance of the modified PIP.

The addition of the 'suppression' screen is made while maintaining the exterior envelope and functionality of the detector. The effectiveness of the suppression screen is characterized in laboratory experiments with an ultraviolet lamp. It is shown that the suppression screen effectively removes the current due to photoemission. Further experiments are conducted in the laboratory plasma chamber to assess the ability of the modified PIP to make measurements in a simulated ionospheric plasma. An attempt is also made to model the effectiveness of the suppression screen in solar radiation at typical sounding rocket altitudes. It is expected that the screen will reduce the photocurrent to a negligible level.

The suppression screen PIP has flown on a technology test flight and made plasma measurements as expected. However, this flight was in darkness, so the effectiveness of the suppression screen in solar radiation could not be verified. The C-REX-2 sounding rocket was scheduled to launch in the winter of 2019. The trajectory of this rocket will be exposed to substantial sunlight and was a significant source of motivation for the addition of the suppression screen. Unfortunately, the launch was delayed a year due to unfavorable ionospheric conditions. Because of this delay the performance of the suppression screen PIP in solar radiation is still untested.