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I would tend to doubt it.  Heh Iran, need a guidance system for your  
missiles?

On Jan 9, 2008, at 3:10 PM, Greg R. wrote:

>
> Wonder if those ANS units have been declassified and are now available
> on the surplus market? Although I think the inertial part of it might
> be a little pragmatic on a sailboat... ;-) (Though maybe it actually
> *could* actually track the various pitching/rolling/etc. movements?).
>
> --
> GregR
>
>
>
> --- Dan Allen  wrote:
>
>>
>>
>> On Nov 28, 2007, at 11:25 PM, Paul Hirose wrote:
>>
>>> Interestingly, that paper says the SR-71 astro-inertial unit had a
>>> catalog of 57 stars. I wonder if those were the same 57 stars
>> listed
>>> in
>>> the nautical almanac.
>>
>> I was reading today in Richard H. Graham's excellent "SR-71 Revealed:
>>
>> The Inside Story" (Motorbooks, 1996) and came across this info where
>>
>> he -- an SR-71 pilot and squadron commander, and retired head of all
>>
>> SR-71s, so he is an authority -- states there were 61 stars in the
>> SR-71 catalog.  Here is an extract from pages 65 and 66 of his book:
>>
>> ---
>>
>> Navigational Systems
>>
>> The SR-71�s high speed and sensitive missions demanded a navigational
>>
>> system that was highly accurate, reliable, and didn�t depend on
>> inputs
>> from other sources subject to electronic jamming. Patterned after
>> navigational systems used on ICBMs, the SR-71�s Astro-inertial
>> Navigation System (ANS) filled those requirements. Simplistically,
>> the
>> ANS was a star tracking navigation system. At least two different
>> stars had to be tracked for optimum navigation performance. With a
>> highly accurate chronometer (to the 100th of a second) supplying
>> Greenwich Mean Time (GMT) and the Julian date, along with a 61-star
>> catalog stored inside the ANS computer, it was possible to know
>> precisely where SR-71 was over the ground.
>>
>> Selection of which star to track was made by the ANS computer a
>> function of latitude, longitude, day of year, time of day, aircraft
>> pitch and roll, and location of the sun. The computer selected a star
>>
>> by going through its star catalog, which was arranged in decreasing
>> star brightness until it found a star. A telescope-like star tracker
>>
>> looked for the stars in an expanding rectangular spiral search
>> pattern. The ANS window was located on top of the fuselage, just
>> forward of the air refueling door and consisted of a round piece of
>> distortion-free quartz glass (about 9 inch diameter) that allowed the
>>
>> star tracker to see through.
>>
>> On the cockpit ANS panel a star �ON� light indicated that a minimum
>> of
>> two different stars had been tracked within the last five minutes.
>> Star tracking was automatic. However, the RSO could assist the system
>>
>> in overcoming conditions such as overcasts, changes of sky background
>>
>> brightness, long periods of ground time, and air refueling when the
>> boom obscures the tracking window. Former RSO, Col. Phil Loignon
>> (Ret), recalls a sortie he flew over North Vietnam that changed
>> future
>> ANS procedures.
>>
>> Jim Watkins and I launched on a operational sortie. We had solid
>> cloud
>> cover to 60,000 feet and no star lock on at coast in. A viewsight fix
>>
>> revealed a position error, so I updated the ANS. After exiting North
>>
>> Vietnam, the �STAR� light came on, and our track showed a 10 nautical
>>
>> mile error. The inquisition hy the 15th Air Force following that was
>>
>> something to hehold. We had flown over Hanoi instead of 10 miles
>> away.
>> Our error had allowed intelligence to determine that a new device on
>>
>> the North Vietnam radar sites was actually an optical device for
>> tracking low level fighters. Although I was thought to have �screwed
>>
>> up,� Lockheed came through with the determinations that the ANS
>> tracked a light bulb in the hangar and had induced a heading error.
>> We
>> changed our ANS turn-on procedures as of that date.
>>
>> By comparing the position of the stars to their known location, and
>> with the exact time of day, the ANS could then compute the aircraft�s
>>
>> precise position. A normal gyro compass alignment of the ANS required
>>
>> 36 minutes of warm-up time and provided the SR-71 with great-circle
>> navigational accuracy of 1,885 feet (0.3 nautical mile) for up to ten
>>
>> hours of flying time. It still amazes me even today that astronomers
>>
>> have charted our solar system so accurately that it allows the ANS to
>>
>> calculate the SR-71�s position so precisely. Things may change here
>> on
>> Earth from century to century, but the same stars guided both
>> Christopher Columbus and Habus.
>>
>> The heart of the ANS was a large, self-contained unit�about half the
>>
>> size of a large refrigerator�called the Guidance Group. A computer
>> inside the Guidance Group computed auto-navigation, guidance and
>> avionics control, and maintained a continuously updated account of
>> navigational status and coordinate values. The computer also stored
>> instrument and mathematical coefficients, predetermined data
>> references that defined the stars, and the mission flight plan. For
>> continuous accuracy. the computer initiated and evaluated self-tests
>>
>> periodically throughout the flight. Software corrections to the star
>>
>> data were provided for the supersonic shock wave over the star
>> tracker
>> window that refracts the star light and for pressure and temperature
>>
>> gradients acting on the window causing optical lens effects.
>>
>> The aircraft�s flight plan and sensor operation for the entire
>> mission
>> were contained on a wide tape punched with holes and loaded inside
>> the
>> Guidance Group computer memory. The tape was made by the 9th SRW�s
>> Mission Planning Branch, a group of highly experienced Air Force
>> officers who knew how to plan SR-71 missions down to the finest
>> detail. Many former SR-71 RSOs worked as mission planners to provide
>>
>> expertise. As the tape ran inside the Guidance Group, the pattern of
>>
>> holes �told� the aircraft where to navigate, what bank angle for
>> turns, when various sensors were to turn ON/OFF, and where to have
>> the
>> sensors �look� for intelligence gathering.
>>
>> Prior to every flight, ANS maintenance personnel loaded the tape and
>>
>> ran the Guidance Group in their shop to insure the programming was
>> correct. The Guidance Group was delivered to the aircraft several
>> hours before flight. It was hoisted up by a crane assembly and slowly
>>
>> lowered into its air conditioned bay located directly in front of the
>>
>> air refueling door. Once inside its bay, numerous electrical, air
>> conditioning, and computer connections were completed, mating the
>> Guidance Group to the aircraft. An exterior aircraft panel containing
>>
>> the star tracker window bolted over the Guidance Group.
>>
>> The RSO had all the ANS controls in his cockpit. On the ANS panel,
>> the
>> RSO had a constant digital readout of longitude and latitude, wind
>> direction and velocity, time to turn, and distance to the next turn
>> point. By use of his keyboard a variety of other information was
>> available from the ANS display panel, such as ground speed and true
>> air speed. As long as everything was working satisfactorily, the RSO
>>
>> monitored the readouts to insure their accuracy. At any time, the RSO
>>
>> could manually override the ANS�s preprogrammed flight path and
>> sensor
>> action points, if required. It was an automatic abort if the ANS
>> wasn�t working correctlv, and since Don had first-hand knowledge of
>> that, he had total responsibility in making abort decisions
>> concerning
>> our navigational accuracy. If we were in clouds or couldn�t achieve a
>>
>> satisfactory star lock-on, the SR71 navigated by an inertial-only
>> guidance system. The inertial system had to be aligned and was
>> updated
>> automatically by the ANS when it was navigating normally. By using
>> fix
>> points every hour, the inertial-only system maintained a navigational
>>
>> accuracy of two nautical miles per hour.
>>
>> ---
>>
>> Exciting!  I wish I had a pocket star tracker.
>>
>> Dan
>>
>>
>>
>>>
>>
>
>
> >



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