329 Parker Solar Probe MAG Boom Design, Analysis and Verification  

Weilun Cheng*, Calvin Kee* and John Wir zburger* 

     Abstract  

For the “ hottest and coolest ” mission to the Sun, FIELDS is the science instrument suite on the Parker Solar  Probe (PSP) spacecraft that measures  the magnetic fields in the solar corona during close approach to the  Sun. The FIELDS instrument suite features five electric antennas and three magnetometers . The   MAG netometer  (MAG)  boom accommodates  all three magnetometers and one of the electric antennas, the  V5 antenna. The unique PSP sun shield – known as  Thermal Protection System (TPS) – generates an  umbra for the spacecarf t and instruments so that the temperature environment is  manageable during close  approach to the Sun. The cone- shaped umbra tapers off towards the bottom of the spacecraft. With the tip  of the deployed boom 3.5 meters aw ay from the bott om of the spacecraft , the umbra imposed a tighter  alignment requirement  for the deployed boom than the instrument pointing requirement . This paper  describes the design, development and verification of the Mag boom. Included are the dynamic analys es  of boom deployment using Ad ams software, and the verification  of the final on-orbit boom deployed position  using the V5 antenna, solar limb sensors, and spacecraft attitude maneuvers.  

Introduction  

Parker Solar Probe is a mission to touch the sun. It is the first- ever mission to get as close as 6.16 million  kilometers  to the sun. The mi ssion is planned for seven years, including 24 orbits around the sun using  seven Venus flybys to gradually reduce the perihelion distance relative to the sun.  The spacecraft is about  the size of a small car. T he thermal protection system on top of the spac ecraft is made from a 11.43- cmthick carbon- composite structure which can withstand temperatures of up to 1,400 degrees Cel sius and  beyond . There are four major  investigations  for the mission: 1)  Fields Experiment ( FIELDS)  is designed to  measure magnetic fields in the solar corona;  2) Integrated Science Investigation of the Sun (ISOIS) will  make observations of energetic electrons, protons, and heavy ions that are accelerated to high energies;  3) Wide -field Imager for Solar  Probe (WISPR) will take images of the solar corona and inner heliosphere,  solar  wind, shocks and other structures as they approach and pass the spacecraft; 4) Solar Wind Electrons  Alphas and Protons (SWEAP) Investigation will count the most abundant parti cles in the solar wind and  measure their properties such as velocity, density, and temperature. This paper focusses  on the  magnetometer boom that accommodates four of the FIELDS instruments.  

MAG Boom Description  

The Parker Solar Probe Mag boom measures 3.5 meter s long. It has two saloon- door style hinges, two  composite boom  segments, four instruments, two connect or brackets, and one harness bundle, weighing  a total of 9.02 kg. It was restrained to the spacecraft with two launch locks, the +Z loc k and the - Z lock. The  two boom segments were made from a layup of M55J/RS3C uni -directional carbon- fiber cyanate ester prepreg.  6AL-4V Titanium end fiitings  were bonded to the boom segments with  Henkel Hysol EA -9360  adhesive. The four instruments included two Fluxgate Magnetometers  (MAGi and MAGo) , one Search Coil  Magnetometer  (SCM) , and one V5 antenna. They  were all  populated on the outward segment of the boom   assembly  to allow maximum distance from the spacecraft while staying within TPS shadow , the umbra .  Each instrument came with a harness pigtail that connected to either of the two connector brackets  based  on where each instrument was located. This a rrangement  allow ed last-minute instrument replacement , if 

* Johns Hopkins University Applied Physics Laboratory , Laurel, MD    Weilun.Cheng@jhuapl.edu , Calvin.Kee@jhuapl.edu , John.Wirzburger@jhuapl.edu 

Proceedings of the 45th Aerospace Mechanisms Symposium, NASA Johnson Space Center, 2020