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Chapter 3 / Sensors / Seeker
_ _
3.9.9 Sensor Limitiations
Provision of seeker range, range-rate, bearing and elevation measurements
at the output interface depends on:
• User target measurement selection ( MS_MSAV2 bits 1 to 4 cleared )
• Range limiting ( SK_SD_ER bit 20 is set )
• Out-of-beam limitations ( SK_SD_ER bit 21 is set )
• Fade ( SK_SD_ER bit 22 is set )
When active, if any of these limitations are violated, bits 1-4 in the
measurement ready flag MS_MSRY2 are cleared. Failure to provide
measurements at the user request is indicated by setting bits 1-4 of
MS_SK_VF depending on the measurements affected. Measurements are
provided if the target range is within [RMIN,RMAX], defaulting to [0.1,5] km.
Failure to provide measurements due to minimum or maximum limiting is
indicated by setting bits 5-6 of MS_SK_VF respectively. Measurements are
also suspended if the target lies outside the ± 2° beam angle (SKξBW),
ξ
SB
S
SB
S
SB
H
3.9-17
H
B
B
A
T : = T ⋅ T ⋅ T ⋅
−1
( ) T S
T
SB SB
( cos ΨS
⋅ cosΘS
) < SK BW
: = cos
ξ
A
Equation 3.9-44
Equation 3.9-45
Failure to provide measurements when the target is not in the beam is
indicated by the setting of bit 7 in MS_SK_VF.
If the detector is being used in strap-down mode the missile boresight to
seeker head angles are zero. If the gimbals are free to rotate the angle
between the detector and beam is zero. For a brief review of Swirling target
models refer to §3.8.8. Failure to provide detector measurements due fade
is indicated by setting bit 8 of MS_SK_VF.
3.9.10 Output Interface
The unsigned range, signed range-rate and target angles are pass through a
16 bit digital interface at a frequency (SKfO) of 400 Hz (clock 9). They are
subject to interface range limits of [0,5000] m, ± 5000 m/s and ± 90°, and a
one-cycle transmission delay.
SK
Z ~
: =
IF
ϕ
TD
IF IF IF
( ( ( ( Z , SK fO
) ) ) )
~
ϕ ϕ ϕ
Q
LIM
ZOH
Equation 3.9-46