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- The Direct Measurement Explorer-A (DME-A) satellite was launched in November 1965 into a near-earth orbit ranging between altitudes of 500 and 3000 km to sample and measure charged particles. The attitude control system is used to keep the spin axis aligned with the orbit normal and to maintain the spin rate. Spin axis control is achieved by a chargeable permanent magnet system which is operated upon command and reacts with the earth's field to produce precession of several degrees per minute. With this system the spin axis was kept within 10 degrees of the orbit normal for several weeks at a time, although larger deviations have been tolerated. The spin rate was observed to decay at 0.05 rpm per day. Periodic use of the spin rate control system has compensated for spin decay. This system is analogous to a DC motor in which the entire satellite is the armature. Group: Platform_Details Entry_ID: EXPLORER-31 (DME-A) Group: Platform_Identification Platform_Category: Solar/Space Observation Satellites Platform_Series_or_Entity: EXPLORER Short_Name: EXPLORER-31 (DME-A) End_Group Group: Synonymous_Platform_Names Short_Name: Explorer-A Short_Name: Explorer 31 Short_Name: 01806 End_Group Group: Platform_Associated_Instruments Short_Name: SPHERICAL MASS SPECTROMETER Short_Name: ELECTROSTATIC ANALYZERS Short_Name: ENERGETIC ELECTRON CURRENT MONITOR Short_Name: ELECTRON TEMPERATURE PROBE Short_Name: MAGNETIC ION-MASS SPECTROMETER End_Group Group: Orbit Orbit_Inclination: 79.80 degrees Period: 119.70 min Perigee: 505 km Apogee: 2833 km End_Group Creation_Date: 2007-12-14 Online_Resource: http://stinet.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0656730 Sample_Image: http://www.daviddarling.info/images/DME.jpg Group: Platform_Logistics Launch_Date: 1965-11-29 Launch_Site: Vandenberg Air Force Base, USA Primary_Sponsor: NASA End_Group End_Group
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