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FINAL REPORT 

BIT MISSION 7060 

25 June 1965 

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FINAL REPORT 

BIT MISSION 7060 

1. **1-6.),.. MISSION SUMMARY. 

1. 1 "1,6),.._ Program Objectives. 

The objective of the BIT program is to determine if and when 

the radar system associated with the signal acquires and tracks 

the Agena vehicle. The BIT system, designed to fulfill this objective, 

covers the frequency range from 153 to 163 Mc to determine if signals 

are present which have characteristics similar to On those 

signals which qualify, the system will measure frequency, PRF, and 

signal amplitude along with the time of intercept to enable an analyst 

to identify the signal characteristics and to estimate a geographical area 

within which the emitter is located. 

1.2 Mission Highlights. 

1. 3 1S).., Flight Summary. 

Vehicle Number 1615 

Launch Date 18 May 1965 

This Docutnent Consists of— Pages: 

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1. 3 -- Continued. 

Launch Time 1802Z, 

Inclination 75 degrees 

Apogee 181.4 nautical miles 

Perigee 109.8 nautical miles 

Period 89.8 minutes 

2. -115).-. MISSION COVERAGE. 

2. 1 Operational Coverage. 

This mission was split into two parts separated by a four.clay 

scheduled "dead" period. The first part lasted 166 orbits and covered 

the period from launch to 0159Z on 29 May. The vehicle was then 

deactivated for 64 orbits until 0135Z on 2 June. Thrs remainder of the 

mission lasted until orbit 264 and was terminated a$ 043()Z on 4 June. 

The BIT system was programmed on during 199 orbits of the 

200 active orbits. On 27 of the orbits the unit was programmed on 

throughout the entire orbit. Data were received from at of the orbits 

with the exceptions of data from orbits 136 through 1411' 161 through 

165, 174 through 175, and 242 through 245. These data were lost because 

the tape recorder which BIT sha'res with the primary payload failed to 

read out when commanded. 

2.2 %*(54. SystemCoverage. 

The BIT system shown in Figure 1, monitors the 154 to 162 Mc 

frequency range with a receiver sensitivity of -55 dbrn, With the inclusion 

of the effects of the antenna pattern with different polarizations and 

aspect anglsis, the overTall detection sensitivity of the cyst :m ranges 

from -58 dbrn to -46 dbm. Signals intercepted by the receiver are 

checked by pulse width qualifier to determine if the pulse width is 

greater thasii25 microsqconds. The pulses which qws.lify are counted in 

a total pulsq counter, PAC, over the commutatpr ree.4.1p iiiiterval of 

400 millisegonds and are measured to determine their amplitude and 

frequengy. On previous systems, the amplitude and frequency 

Ineasuremerts also required PRF qualification but on this 4nit the PRF 

Qualifier is bypassed. It is, however, still used to accurately check 

the PRF to determine if it falls within the 94 to 100 pps acceptance band 
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2. 2 -- Continued. 

or harmonics of this range. If a signal has a power level at the receiver 

in excess of -30 dbm, its amplitude will be measured in the PLD-A channel 

regardless of PRF or pulse width. The RF frequency of the high amplitude 

pulses will not be read unless the signal also satisfies the pulse width 

criterion. 

3. MISSION RESULTS. 

3. 1 PRF Qualified Intercepts. 

3. 2 "'""j•S)....„ Non Qualified Intercepts. 

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3. 2 (S).., -- Continued. 

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3. 2 (`S.) -- Continued. 

4. SYSTEM PERFORMANCE. 

4. 1 TS.L System Specifications. 

A summary of the system specifications for the BIT system used 

on this mission is given below. The block diagram of the system is 

shown in Figure 1. 

Minimum Detectable Signal -55 dbm PLD-B 

-30 dbm PLD-A 

Minimum Acceptable Pulse Width 25 microseconds 

PRF Qualifier Range 94-100 pps 

188-198 pps (2nd Harmonic) 

RF Passband 

-52 dbm 

-25 dbm 

4. 2 ...11S)L System Operation. 

154.4 to 161.4 Mc 

147.0 to 170.3 Mc 

The BIT system appeared to function normally throughout the 

mission with the exception of a failure in the Time Reference Generator 

(TRG) which occurred approximately 30 minutes after launch. This unit, 

built by the Adcole Corporation, apparently sufferred a failure in the 

binary countdown chain which resulted in an erratic doubling of the counting 

rate just prior to complete failure. As a result of this failure, the BIT 

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4. N. -- Continued. 

Signal Simulator was disabled because it requires a start trigger from 

the TRG. Thus, the operation of the BIT circuits could not be checked 

after the failure. The system response to the Simulator prior to the 

TRG failure showed that all of the circuits were functioning properly. 

The primary function of the TRG is to provide a time base from 

which event times can be established. Because of the failure, the event 

times for the orbit 23 intercept had to be determined by interpolation 

between the turn on and turn off times of the system and recorder on that 

orbit. These times are determined by the primary program organization 

and are accurate to within one second. Thus, the accuracy of the intercept times depend only on the magnitude of tape recorder speed variations 

during the tape recorder read in and read out periods. Comparing the 

time required to read out the data from orbit 23 with the programmed 

duration of the read in shows that the recorder operated at its specified 

26 to 1 playback to record ratio. This ratio was also observed in the 

data prior to the TRG failure. It is therefore concluded that any speed 

variations were minor and averaged out to zero. The interpolation 

process should then enable determining event times to within approximately five seconds. 

4. 3 *****)„.. System Testing. 

Because of the interference observed during this intercept, it 

was decided to perform a series of laboratory tests on one of the unused 

BIT systems to determine the conditions which would produce the effects 

noted in the data. It was found that the amplitude and frequency measurements are only affected when a narrow interfering pulse is received 

simultaneously with a wide qualifying pulse. Under this condition, the 

amplitude measurement will increase by an amount which is a function 

of the relative amplitudes of the two pulses and the frequency measurement will correspond to the frequency of the narrow pulse only if its 

frequency is lower and its amplitude is greater than those parameters 

of the wide pulse. See Figure 4. 

Based on the results of the test it can be stated that the frequency 

measurements are valid; however, the measurements of the interfering 

signal must be identified and separated from the desired measurements on 

the This was no problem during the scanning mode of Part I 

because the interference did not completely mask the measurements on 

the 11111111 . 

scan. It was, however, a problem in Part II since only the 

155 Mc frequency measurements are present. In the latter case, either 

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4. 3 ***ISL -- Continued. 

the interference completely masked the 

it always hada greater amplitude and the 

above 156 Mc or, more probably, the 

making the separation of the two impossible. 

measurements because 

frequency always remained 

stopped its scan at 155 Mc 

The tests also showed that the amplitude of the signal 

cannot exceed the measured levels and it is probable that the actual 

amplitude of 3 to 9 db below the measured values. This 

is because the interference amplitude adds to the amplitude to produce 

a resultant measurement which is greater than either of the components. 

For example, when the two amplitudes are equal, the measured value of 

signal level is 6 dbm higher than the level of the qualified signal without 

the simultaneous pulse interference. 

Tests on the Pulse Width Qualifier and the total pulse counter (PRC) 

showed that it would not respond to the narrow pulse interference except 

under two conditions. One condition requires that two or more narrow 

pulses each have sufficiently wide widths and occur close enough together 

so that the resulting group of pulses has sufficient energy to charge up the 

PW integrator until it exceeds the qualification threshold. This condition 

rarely occurs for it generally requires three pulses with 8 to 10 microsecond 

widths occurring at 3 microsecond spacings before it appears to the PW 

Qualifier as a single 25 microsecond pulse. The sec6nd condition requires 

a PW qualified pulse train having widths greater than 40 microseconds 

and narrow, interfering pulses. If a narrow pulse of sufficient width 

occurs just after the trailing edge of the wide pulse an additional pulse 

count will result. To produce this effect, a pulse width of at least 4 

microseconds is required. The spacing is 3 ±0. 5 microseconds for the 

minimum 4 microsecond pulse width and increases as the pulse width of 

the interference increases. Since the requirements for the width and 

position of the narrow pulse with respect to the wide pulse are rather 

critical, the requirements will be only occasionally satisfied in the 

general signal environment. EVen under the worst case, where the 

narrow pulses are synchronized with the wide pulses, the pleasured pulse 

count would only be twice the count of the wide pulses. During this 

intercept, something more complex than noise or narrow pulse interference 

occurred to cause the PRC to register values between 3Q 44c1 130 pps. 

The tests on the BIT system also revealed th4 pLP-A could be 

influenced by p.oise spikes passing through the receivrr. A condition, 

similar to that noted during this intercept, was olserve4 when a noisy 

cqmmutator was used with the system. As soon is a signal was present 

in the receiver, the noise spikes drove PLD-A to a level corresponding to 

approximately -20 dbm regardless of the input signal level. This level 

remained conotant until the signal level exceeded the -20 dbrn level at 

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4. 3 154„..... - Continued. 

which point PLD-A then responded to the higher amplitude signal. Apparently, 

during this intercept, noise spikes were being generated at approximately 

two second intervals by something on the vehicle. This caused PLD-A to 

indicate a constant signal level of -19 dbm, during the entire 250 second 

interc ept. 

4. 4 System Modifications. 

Corrective action has been taken to significantly reduce the 

susceptibility of the two remaining BIT systems to the interference 

generated by simultaneously receiving a non-qualified pulse with a qualified 

pulse. The Recognition Logic was modified such that the amplitude and 

frequency Peak Level Detectors would open for only 20 microseconds 

rather than for the entire pulse duration. The 20 microsecond mono stable 

multivibrator in the PRO is now used to control the gates. This modification 

was readily accomplished because the PRF Qualification requirement had 

been previously eliminated on an earlier modification. Tests show that this 

change virtually eliminates the type of interference observed during this 

mission since PLD-B and PLD-C are now open for only 20 microseconds 

rather than for the pulse duration. Thus, interference can only occur if 

a narrow pulse falls within the 20 microsecond gate. 

The response of PLD-A to noise spikes was also greatly reduced 

by decreasing the rise time of the circuits from approximately 0. 5 microseconds to approximately 2 microseconds. This eliminated the simulated 

interference and will, presumably, reduce or eliminate actual interference 

on future vehicles. 

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5VECIAL IIANDLINC