{"id":1604,"date":"2010-07-12T12:11:46","date_gmt":"2010-07-12T16:11:46","guid":{"rendered":"https:\/\/wpmu2.mit.local\/?p=1604"},"modified":"2010-07-19T11:27:23","modified_gmt":"2010-07-19T15:27:23","slug":"development-of-a-micromachined-retarding-potential-analyzer-for-sensing-plasma-conditions-at-spacecraft-re-entry","status":"publish","type":"post","link":"https:\/\/wpmu2.mit.local\/development-of-a-micromachined-retarding-potential-analyzer-for-sensing-plasma-conditions-at-spacecraft-re-entry\/","title":{"rendered":"Development of a Micromachined Retarding Potential Analyzer for Sensing Plasma Conditions at Spacecraft Re-entry"},"content":{"rendered":"

To ensure safe operation during space missions, NASA is sponsoring research on advanced sensing systems.\u00a0 In this endeavor, one particular facet is the development of a sensing skin that would monitor the spacecraft re-entry conditions.\u00a0 A retarding potential analyzer (RPA) is a device that would provide useful information about the ion energy distribution of the plasma that forms around the spacecraft while it re-enters the atmosphere.\u00a0 As a consequence of the harsh conditions during re-entry, the sensor must be made of suitable materials such as silicon carbide or tungsten. \u00a0We are currently developing a hybrid MEMS-macro RPA that uses grids made of either bulk silicon coated with SiC or W. Design constraints of the RPA require closely packed holes with large aspects ratios. Therefore, the grids are etched using deep-reactive-ion-etching (DRIE).\u00a0 We plan to investigate the effects that various probe parameters have on the RPA\u2019s performance, which is driven mainly by the Debye length of the plasma [1<\/a>]<\/sup>.\u00a0 To this extent, the hybrid sensor has been designed to allow variations in grid hole diameter, pitch, and transparency.\u00a0 Limitations in grid-to-grid spacing will also be examined.\u00a0 The modular assembly of the device is shown in Figure 1.\u00a0 Based on this experimental exploration, a fully micromachined RPA will be built using a MEMS 3D packaging technology that we pioneered for multiplexed high voltage MEMS [2<\/a>]<\/sup> [3<\/a>]<\/sup>.\u00a0 An example of what this MEMS RPA may eventually look like is given in Figure 2, where the first grid is shown on the left and the collector plate is displayed on the right. The proposed MEMS RPA has five electrodes to insure proper data collection.\u00a0 Future work will further reduce the footprint of this final design as well as explore the possibility of machining the grids using bulk SiC.<\/p>\n\n\t\t