THEMIS MISSION PREENVIRONMENTAL REVIEW DC MAGNETICS Michael Ludlam

THEMIS MISSION PRE-ENVIRONMENTAL REVIEW DC MAGNETICS Michael Ludlam University of California - Berkeley MPER DC MAGNETICS 1 UCB, June 23, 2006

Introduction • Results from FM 2 • Component Magnetics • Requirements • Test Procedure • Facilities MPER DC MAGNETICS 2 UCB, June 23, 2006

FM 2 Tests Testing on FM 2 probe was very successful. MPER DC MAGNETICS 3 UCB, June 23, 2006

FM 2 Data • • MPER Two sets of measurements were made: • pre-environments • post-environments This was to check the environmental tests did not affect the spacecraft magnetic moment as well as to verify requirements. From the post environments tests: • Maximum field measured at distance of the magnetometer was 2. 8 n. T. Requirement is 5 n. T. • However this field is not uniform in the radius of the distance of the magnetometer. At the location of the magnetometer the field is much smaller, 0. 5 n. T. • Variance of the field from having the spacecraft powered or induced by field changes is within the 0. 1 n. T requirement. A comparison of the pre-environmental data and post environmental data showed the spacecraft field decreased. Although the reason for this is unknown (but possibly from the deperming coils from the shaker table), the variance in the field is very small at the FGM (0. 2 n. T). DC MAGNETICS 4 UCB, June 23, 2006

Component Magnetics Testing Status of Probe components: • All Instruments including IDPU have been magnetically mapped. Some bus components have been mapped – BAU, AEB, Battery, Transponder as available. • IDPU has been degaussed to deperm magnetic SMA connectors. • Baseplate with RCS piping and valves have not been degaussed – a known magnetic offender with latch valves. This is the main reason for needing to deperm the spacecraft. • The units tested are ‘in family’ with those measured for FM 2. MPER DC MAGNETICS 5 UCB, June 23, 2006

Issues Found Two issues with probe components discovered since first JPL visit: • FM 2 Battery was delivered to UCB by third party courier. During the incoming magnetics survey, the battery was found to have higher moment than measured during battery deperming at GSFC. The battery was depermed and installed onto the FM 2 Probe. Qualification battery was resurveyed to see if the chargedischarge cycle was causing the batteries to perm up. QM was magnetically clean. Therefore, the most likely explanation was that the FM 2 Battery was permed up by an external source during shipping. All other batteries were shipped with the probes in a controlled environment. • A check of the balance mass proposed by SAI was found to be magnetic. An evaluation of the materials list showed the Tungsten alloy included Iron and Nickel. New balance mass material procured. MPER DC MAGNETICS 6 UCB, June 23, 2006

Test Flow Testing at night. Plan is to survey and deperm one probe per night. As received survey Deperm Spacecraft Post deperm survey MPER DC MAGNETICS 7 UCB, June 23, 2006

Requirements from Magnetics Contamination Control Plan (THM-SYS-002 D) derived from the Mission Requirements Document (THM-SYS-001). • 5 n. T spacecraft field at location of FGM (M 31 a). • Stability of spacecraft field shall be less than 0. 1 n. T over 12 hours at the location of the FGM (M 31 b). This was tested on the FM 2 probe and will not be measured this time around. MPER DC MAGNETICS 8 UCB, June 23, 2006

Test Procedure MPER • Test Procedure written by Pablo Narvaez (JPL) incorporating UC Berkeley DC Magnetics test procedure originally written for the purpose. • THEMIS Probe DC Magnetics Test Procedure (JPL D 33980). • Procedure is ready. A subset of tests run on FM 2 will be run on the other probes. DC MAGNETICS 9 UCB, June 23, 2006

Facilities • • • MPER DC MAGNETICS 10 Testing of FM 2 during the night was quicker than expected, and the field stability was good. UCB provided MGSE for holding probe worked well. No modifications are required for the next round. Facility worked well for FM 2 UCB, June 23, 2006

Magnetic Survey Vertical Mapping Setup Horizontal Mapping Setup Location of magnetometers: 1. 5 m from cg (for Analysis) and 2 m from edge (FGM location) MPER DC MAGNETICS 11 UCB, June 23, 2006

Deperming done using slowly varing DC field whilst probe is rotated in the x-y plane. The deperm is repeated in the x-z plane. The maximum field for the deperm will be 15 Gauss. If this does not achieve good results, it is possible to increase this to 20 Gauss. MPER DC MAGNETICS 12 UCB, June 23, 2006

Test Personnel Pablo Narvaez – JPL Ellen Taylor – UCB Michael Ludlam – UCB (by phone) MPER DC MAGNETICS 13 UCB, June 23, 2006

Summary Results from FM 2 were excellent. Expectation is that other probes will be similar from initial component testing. Component Magnetics • All units are ‘in family’ Facilities • JPL DC magnetics coil facility is ready. Requirements to verify • 5 n. T spacecraft field at location of FGM. Test Procedure • MPER THEMIS Probe DC Magnetics Test Procedure (JPL D-33980) is ready. DC MAGNETICS 14 UCB, June 23, 2006