WISPR Details

Design Philosophy

The WISPR design draws its heritage from the SECCHI heliospheric imagers aboard the Solar Terrestrial Earth Relations Observatory (STEREO; Kaiser et al. 2008) mission and from the SoloHI imager (Howard et al. 2013) under development for ESA’s Solar Orbiter mission scheduled for launch in 2017 (Müller et al. 2013).

System Description

The WISPR instrument comprises two modules: (1) the WISPR instrument module (WIM), shown in Fig. 9, includes the structure, baffles, door, telescopes, focal plane arrays (FPA) and the camera interface electronics (CIE), and (2) the Instrument Data Processing Unit (IDPU) which consists of the Data Processing Unit (DPU) and the Low Voltage Power Supply (LVPS). The electronics functional block diagram is shown in Fig.

Assembly, Integration and Test

The instrument is calibrated at the component and subassembly level as well as “end-to-end” at the instrument unit level. Optical tests will ensure that the baffle surfaces and optical components meet requirements for efficiency, imaging and scattered light. The APS detector is calibrated for quantum efficiency, dynamic range, resolution, and noise. The instrument performance is tested/characterized in the dedicated NRL coronagraph test facilities that contain an 11 m beamline optical test chamber and Class 100 cleanroom.

Environmental Challenges

We have little, if any, information for the environment PSP is going to operate in. It is reasonable to expect that the spacecraft will encounter high particle intensities, including elevated numbers of neutrons. The mission total ionizing dose (TID) of radiation is estimated to be 24 krad behind 100 mils (2.54 mm) of Al shielding.

Radiation Effects

We used PSP radiation guidelines for a seven-year mission for EEE parts selection. Our designs address single event effect (SEE) induced failure (latchup, burnout, gate rupture, secondary break-down), non-destructive SEE (e.g., non-destructive latchup, minilatchup, and single event functional interrupts) and single eventinduced soft errors (including single event upsets (SEU) or transients in linear devices) and SEE-induced soft errors.

Effects of High Speed Dust Impacts

Given the potentially high dust velocities, the kinetic energy distribution and fluence of the dust particles must inform the instrument design. Since the mass and size distribution is unknown close to the Sun, the design relies on the JHUAPL/UTEP models developed specifically for PSP (Mehoke et al. 2012). The model predicts about 100 impacts from 10- micron particles and 1000 impacts from 0.1-micron particles at the heat shield during the seven years of the mission.