Table 4

Designation EMR Type Photo Cathode Window Material Minimum Background-Nmin (per 14 sec) Maximum Background-Nmax (per 14 sec, outside SAA) R(Nmax/Nmin) Corr Factor

U1 FUV KBr -- 17 80 4.7 1
U2 FUV KBr -- 12 60 5.0 1
U3 G08 CsI LiF 8 42 5.2 1
V1 N09 Bialkali MgF2 3,500 11,000 3.1 0.52
V2 N09 Bialkali MgF2 2,000 7,500 3.7 0.68
V3 D01 Bialkali 7056 Glass 2,500** 4,500 1.8 0.20

Designation Carriage No. Spectrum Order Wavelength (Å) Non-grating Optics Behind Common Entrance Slit

U1 1 2 710-1500
U2 2 2 750-1645 Dipping Mirror
U3 Fixed 1 1310 Å Blackened reflecting mirror
V1 1 1 1640-3185 Fabry optics (reflecting), quartz filter
V2 2 1 1480-3275 Dipping mirror, Fabry optics (incl. sapphire prism)
V3 Fixed 1 3428 Å Reflecting mirror

Designation Scaling Factor Operating Voltage* Typical 14-Sec Dark Count
Earth Vacuum Tests, -2°C

U1 21 4.9 KV 2.0
U2 23 4.9 KV 2.8
U3 25 3.0 KV 1.4
V1 22 3.0 KV 9.1
V2 24 3.0 KV 14.2
V3 25 3.0 KV 140

General Pulse Counting Characteristics

Minimum signal .1 mv U1, U2
.2 mv V1, V2
Shielded in stainless steel tubular shields, 1/8" wall thickness (1/16" for U1, U2).
Preamp & Coupling in spectrometer; amp-discriminators & DG, RSCR in bay C4.
Pulse duration 10 n sec.
Scalars not reset.
Max count rate: 105 Hz.
Pulse resolution (10:10) = 2.5 micro sec.

* Photocathode grounded.

** Where counts in other tubes are low, the V3 count rate may be as high as 7500/14 sec, in orbits where the satellite has just passed the SAA.


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