The Galileo Energetic Particles Detector
Galileo EPD Handbook
Chapter 1. Instrument Summary
LEMMS Subsystem Overview (continued)
Source: W. Studemann, SDO/PAO, Jan. 20-21, 1981
Figure 1-50 shows the pulses from the C, D and the E2 channels as they were measured on the engineering model. These are bipolar channels. The pulses are about 900 nsec long. The top traces show the discriminator outputs for the pulses that appear below them. The E2 channel pulses are from the anticoincidence channel output. There is a 40 to 50 nsec delay in the response of the discriminator. A strobe is delayed off the front edge of the pulse a fixed amount of time. All of the pulses pass through the discriminator on the strobe which occurs in the center of each pulse so that the data is collected from the center of the pulse rather than the edges.
Figure 1-50. Pulses from the C, D, and E2 channels as measured on the engineering model.
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Channel C. 23° C; 1.3 mV/keV |
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Channel D. 23° C; 1.3 mV/keV |
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Channel E2. 23° C; 2.625 mV/keV |
Figure 1-51 shows two successive pulses from channel C. When the discriminator fires, a one shot times out for the length of the pulse. If the next pulse occurs before the one shot time out, it can trigger and start the timing process over, so that the last pulse becomes shorter. At some time interval that has yet to be determined, the second pulse will be missed. In the bottom photograph in Figure 1-51, the pulses are separated by 800 nsec, and only one discriminator pulse is present. In the top photograph, the pulses are separated by 1 microsecond and a second discriminator pulse is present. Two full pulses appear in the middle photograph, when the pulses are separated by 1.2 microseconds.
The photographs in Figure 1-52 show the unipolar pulse outputs from channel E1. Unipolar shaping was chosen for noise considerations. (The noise from a unipolar pulse is lower than the noise from a bipolar pulse of the same duration.) The pulses shown are roughly 900 nsec long, and correspond to H200 keV deposited energy.
Figure 1-51. Channel C pulses.
Figure 1-52. Unipolar pulse outputs from channel E1.
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Updated 8/23/19, Cameron Crane
QUICK FACTS
Mission Duration: Galileo was planned to have a mission duration of around 8 years, but was kept in operation for 13 years, 11 months, and 3 days, until it was destroyed in a controlled impact with Jupiter on September 21, 2003.
Destination: Galileo's destination was Jupiter and its moons, which it orbitted for 7 years, 9 months, and 13 days.