DUST DETECTOR for SAL Design Review Documentation 22 May 1996 revised: Sept 1996 revised: Nov 5 1996 ------------------------------------------------------------------------- ------------------------------------------------------------------------- A. Electrical & TM ------------------- NOTE: Connector numbering has changed since last revision 1. Pinouts and connector of NASA interface: --J1-- The NASA interface to the electronics box (only) is a 25-pin D connector. 25P on the box, 25S on the cable. Pinout: () = pin # +28 (14) (1) +28RET GND (15) (2) GND GND (16) (3) GND GND (17) (4) GND TMUNHHK5(18) (5) NC TMUNH3 (19) (6) TM:apogee TMUNH1 (20) (7) TMUNH4 TMUNH5 (21) (8) TMUNH2 TMUNHHK1(22) (9) TMUNHHK2 TMUNHHK3(23) (10) TMUNHHK4 GND (24) (11) GND maj fr c(25) (12) NC (13) min frm clk Power requirements: +28V@200 mA Comments: --1) We need to reset our integrators after they have been read. Since the UNH data are read near the end of every 4th subframe, we intend to use every 4th minor frame strobe as a reset signal. We need the major frame clock for alignment to the correct subframe. --2) TM and HK are all analog signals. --3) Specifications for power return: twisted pair --4) Pins 15,16,17,2,3,4,24,and 11 (all GND) can be all tied together, with one wire leading through the harness to the signal ground point. This is separate from the +28RET wire. --5) NASA-built harness. --6) The apogee signal should be at 0 V until apogee and +5V after apogee. 2. Pinouts & connector descriptions for experiment-to-experiment harness: We have three inter-experiment harnesses 1) Two connectors between the Faraday detector and UNH electronics and 2) spacecraft potential signal measured by the E-field booms runs from the Cornell electronics box to the UNH electronics. Electronics box to detector box: --J2-- Connector: 15 pin D connector UNH-built. --J3-- Connector: 9-pin D connector UNH-built Spacecraft potential from E-field booms: The Cornell E-field experiment will supply the Faraday sensor with a floating potential signal. This signal is the average of the 4 E-field spheres. The floating potentials are integrated with a time constant of approximately 500 msec. The output is differential with the two sides being (1) the time- and space-averaged floating potential of the spheres and (2) the E-field instrument ground. The connection to the UNH instrument is of very high impedance. --J4-- Connector: DEM9P on each end of harness. Harness: Twisted shielded pair Pinout: (1) Cornell instrument ground (2) Spacecraft floating potential (6) Shield ground; connected at UNH end only 3. No Pyros are required. 4. Timing events Apogee signal to pin (6) of NASA connectors J1. We need this to change our operating mode on the downleg. We can be turned on before launch, as we have no high voltages. 5. HK required in addition to your housekeeping words. i.e. temperature monitors, boom deployment monitors. We have no requirements for these at our end, although NASA may want to have, for instance, a temperature monitor for their own purposes. 6. Power requirements: input current +28 200 mA B. Mechanical: -------------- 1. Mass: Faraday sensor 3 kg electronics box 5 kg 2. MOI estimates: Faraday sensor center of box electronics box center of box 3. Drawings of the experiment including drill patterns for NASA can be obtained via anonymous FTP. The electronics box and Faraday drawings are included with this document. Drawings dust1.eps, dust2.eps, and dust3.eps are of the Faraday sensor; drawing dusteb.eps is of the electronics box. ftp unhggs1.sr.unh.edu user anonymous passwd yourname cd pub/lynette get dust1.eps dust2.eps dust3.eps dusteb.eps bye Note re drill patterns: The Faraday sensor floats with respect to the spacecraft ground. The sensor 'ground' is controlled by the connection from the E-field booms. The sensor is insulated from the deckplate by a thin plastic plate. The connection to the deckplate itself is made with metal screws through the metal flange and plastic plate, with insulated grommets. The plastic plate will be fabricated by UNH. Note: Since the Farday sensor is not at spacecraft ground, it needs to have at least several mm clearance between it and any other surface (i.e., bulkhead or SALMS electronics box.) If the other surfaces might vibrate against the sensor, they should be braced away using insulated materials. Also note: The sensors are connected to the electronics box via connecting harnesses which must pass through the deckplate. The holes must be big enough to pass a 15-pin D connector. We would like this connecting harness to be as short as possible. The connector on the electronics box will be on a 5"x5" side. We need clearance for this connector. C. Other: ---------- 1. Magnetic fields: None. Magnets in the original detector design have been replaced by biased electrodes. 2. Angle of attack (AoA, or Qe requirements): The sensitivity of the dust detector is a nonlinear function of the angle between the velocity vector a vector normal to the deck. Optimally, we wish this angle to be 0 degrees. Realistically, we find: design goal: +/- 2 degrees AoA+coning full signal 5 degrees AoA+coning 5 % loss 7 degrees AoA+coning 7 % loss 10 degrees AoA+coning 25 % loss 15 degrees AoA+coning 50 % loss There is a catastrophic increase in the loss at more than 10 degrees AoA+coning.We think that we can compromise to a resulting (Angle of Attack) + (coning angle) less than 7 degrees, with a 'minimum success' of 10 degress AoA+coning. This translates into a restriction of the Qe, according to calculations done by WFF based on the 41.004 payload mass properties, of 82 degrees < Qe < 84 degrees. This means that a Qe of 82 degrees (yields AoA = 3.2 degrees at 85 km) is acceptable if the coning angle is less than 3.8 degrees. 3. Downleg attitude: We would prefer to optimize the angle between the velocity vector and the spin axis so that it is nearest zero as we go through the dust layer. This is expected to be between altitudes of 80 to 90 km. D. Contacts: ------------- Dr. Kristina Lynch, Co-Investigator Space Science Center Univ. of New Hampshire Durham, NH 03824 (603) 862 3871 (603) 862 0311 (fax) kristina.lynch@unh.edu Lynette Gelinas, Graduate Student Space Science Center Univ. of New Hampshire Durham, NH 03824 (603) 862 4368 (603) 862 0311 (fax) lgelinas@unhedi1.sr.unh.edu Eugenio Sartori, Engineer Space Science Center Univ. of New Hampshire Durham, NH 03824 (603) 862 3238 (603) 862 0311 (fax)