Posted on August 12, 2021
Former WISPR Principal Investigator
Naval Research Laboratory/Johns Hopkins Applied Physics Laboratory
In spite of the uniqueness of the Parker Solar Probe mission, the design of the Wide-field Imager for Solar Probe (WISPR) instrument was not very unique. Part of that was due to using an edge of the spacecraft’s heat shield (Thermal Protection System, or TPS) as the first baffle of the instrument. That allowed WISPR to be in shadow and yet still see very close to the solar limb. Being in the shadow made a very benign thermal environment, and dust-impact testing showed that the usual lens types would be quite acceptable. The biggest challenge for WISPR was that it needed to be small and very low mass. This meant we had to put the rear of the lens assembly very close to the detector surface; that was probably the biggest technical risk. The use of the TPS as the first baffle was complicated in that it wasn’t a common interface, but the spacecraft engineers handled it well (although I’m sure it was a headache).
In addition to providing a large-scale imaging perspective, the spacecraft would fly through regions that we had been observing remotely from Earth and thus would provide extremely high resolution of small structures, which were not observable from 1 astronomical unit, which is the distance between Earth and the Sun. But we also wanted to image more than 90 degrees from the solar vector to see the electron scattering from the solar wind close to the spacecraft.
The historic nature of the mission began to really sink in about a year before launch, with the name change from Solar Probe Plus to Parker Solar Probe. That was an unusual move prior to launch, but it emphasized the impact that the mission would have. I remember Guenter Brueckner saying that any time you can gain a factor of 10 or so in any parameter, you will make a significant, perhaps unexpected, advance. We have already made significant discoveries and we will have many more in the orbits to come.
Russ Howard (at right) and family view the Parker Solar Probe spacecraft during a 2017 event at the Johns Hopkins Applied Physics Laboratory.