1. According to multiple sources, the first AMTI (airborne moving target indicator) radar, admittedly a noncoherent implementation, was operational by the end of WW II. On source identifies it as the AN/APS-27, an airborne search radar developed by the MIT Radiation Laboratory under the name "Project Firefly".

    No source, however, indicates which aircraft its was operational on. I do know it was used on several post-war aircraft including the B-52, RB-66, C-130 and C-135. But that is all.

    Can anyone out there help me run down this obscure bit of history?

    John R Delaney
    MIT Lincoln Laboratory
     
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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  3. Colin1

    Colin1 Active Member

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    Hi
    you'll get spammed to bits with a forum handle like that
     
  4. That is the document which mentions Project Firefly as having developed the AN/APS-27 (from the AN/APS-23), saying "At the end of the war it was operational but had deficiences[sic]". No mention of a TBM in that paragraph but I could certainly believe it was fielded on one. They seemed popular platforms for early airborne radars.

    Thanks again,

    John

    PS We have an industrial-strength firewall here. Its main failing is catching stuff that ins't spam, not letting spam through.

    J
     
  5. HoHun

    HoHun Active Member

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    Hi John,

    >According to multiple sources, the first AMTI (airborne moving target indicator) radar, admittedly a noncoherent implementation, was operational by the end of WW II.

    Are you aware of the British "Fishpond" (ab-)use of their H2S ground mapping radar that showed airborne targets on the ground mapping screen? I'm not sure if this technically satisfies the definition of an AMTI, but I thought I'd mention it anyhow.

    (I believe H2S was designated H2X in US use, but I'm not aware of the AN/APS numbers associated with it.)

    Regards,

    Henning (HoHun)
     
  6. red admiral

    red admiral Member

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    There were multiple versions of H2S. H2S on the S-band at 10cm, H2X on the X band at 3cm and a postwar British set on the Q-band at around 1mm.

    H2X was AN/APQ-13 in US usage.
     
  7. pbfoot

    pbfoot Active Member

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    If I remember correctly MTI to work effectively need PRF or Pulse repition frequency whereby the frequency of the Radar is staggered by a couple of hundred HZ rather then having a steady pulse. I could be wrong as this was part of the course of radar I took andd my memory may be faulty after 30 tears
     
  8. Glider

    Glider Well-Known Member

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    My understanding was that the first operational airborne radar was the AN/APS 20 which was operational during early 1945.

    I have heard of attempts by the RAF to use this type of equipment before this but it didn't work, if indeed it existed or what they used.
     
  9. red admiral

    red admiral Member

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    The RAF undertook a number of experiments with long wave radar (1.5m I think) and dorsally mounted rotating antennas on Wellingtons. So far as I can remember, the radar itself worked ok, the problem was getting a useful output to report position or vector in other aircraft given the limited processing technology. The RAF briefly looked at centimetric radar in a similar installation later but it was agreed that the US should pursue that development. I have a fair amount of information on the earlier efforts if anything wants to be looked up.
     
  10. Glider

    Glider Well-Known Member

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    I remember that they used a Wellington so it looks as if we have the same thing in mind.
    I was given A Radar History of World War II at Christmas and it has wetted my interest. Can I ask what book you would recommend about early Radars in particular AEW? Any hints welcome
     
  11. To Glider for his mention of the AN/APS-20.

    The delay was caused by the need to do some research. Steeljaw Scribe at Steeljaw Scribe: History of AEW: Project Cadillac II (Part One)
    states that the AN/APS-20 was the first AEW radar and an AMTI radar.

    The former is true; the latter is not. A least that seems to be the case after consulting a 1946 publication "Five Years at the Radiation Laboratory" (reprinted by the IEEE in 1991) as well as the Dickey, Labitt, and Staudaher IEEE paper mentioned earlier by FlyboyJ.

    It also appears that AMTI was sensitive subject in 1946. The names of two such radars were "redacted" for security reasons in "Five Years". So the answer to my question is probably buried in immediate post-war classified files. While those files were likely declassified years ago, the information does not seem to have filter bout to the Web or to publications I can earily access. Sigh...

    John
     
  12. Glider

    Glider Well-Known Member

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    The An/APS20 certainly became an AMTI radar probably from the time it was moved from the TBM to the Gannet in the RN/Skyraider in the USN. The main difference between being an AMTI or not seems to be in the communications suite carried on the aircraft not the actual radar.
    Basically the same Radar continued to be used by the RAF in the Shackleton until 1991.
    We Brits do tend to try and get value out of the kit we buy from the USA.
     
  13. red admiral

    red admiral Member

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    AN/APS-20 might have been the first _production_ AEW radar, but definitely not the first per se.

    I forgot to look in the library today, but there are a couple on the subject. The one with lots of detail on early AEW is a collection of technical papers rather than an actual book.
     
  14. The communication's suite on an aircraft has nothing to do with the on-board radar being an MTI radar or not. It is the guts of the radar which matter; the waveforms(s) transmitted and the processing of the returned signal.

    If you want to use an AMTI-equipped aircraft in a GCI-type manner, then extra communications equipment helps. Ditto if you want to relay the AMTI radar's PPI display to a surface ship (a feature, I believe, of the PB-1W).

    As it happens, I have done a little more research, this time in Henry Guerlac's 1947 book, "Radar in World War II". Guerlac was the official historian at the Radiation Laboratory. In his description of Project Cadillac, the origin of the AN/APS-20, he does refer to the AN/APS-20 as an AMTI radar. However, a little later in the book, he reviewed MTI radar development and explicit said MTI radar was still under development on V-J day. Could be the truth or could be OPSEC. I can't tell.

    John
     
  15. Glider

    Glider Well-Known Member

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    No worry, I have been wrong before and will no doubt be wrong again in the future and am always happy to be corrected. Its how we learn.
    In my defence the same basic radar was used in the TBN and the Shackleton which was a stand alone direction control aircraft as was the Gannet, hence my (incorrect) assumption. I know there were a number of upgrades in the 45 year life of the basic design I presume one of those must have covered this requirement.

    Thanks for putting me straight.
     
  16. red admiral

    red admiral Member

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    The book I was thinking of was "Radar Development to 1945" Edited by R.W. Burns

    I had a quick read of one of the AEW pieces as well. There weren't really any unsolvable technical problems with the long wave 1.5m set used on the initial Wellington. The problem was that is was envisioned as being for Air Controlled Interception and for detection of surface ships/submarines. When it was beginning to work, the effectiveness of LW radar against submarines dropped with the appearance of passive warning systems on U boats. As a result research shifted towards 10cm sets, which began to appear in 1942 for experiments. There isn't a great deal of information available on those, other than they preceeded Project Cadillac. It also mentions that the sets were used late in the war to great effectiveness against E-boats, vectoring in MTBs when the system had matured a bit more (north stabilised ppi, half the weight etc..)
     
  17. Glider

    Glider Well-Known Member

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    I have found some information on the use of Wellingtons late war and its a little surprising.
    612 squadron used them during the D Day landings to protect the sea routes for the invasion. So far not exceptional. 524 squadron used the Wellington of Denmark. They acted as pathfinders for the strike wings and a solitary attack took place on the 6th April when a Wellington attacked the E Boats with 250lb airburst bombs which must have been deadly against the unprotected Boats.
    The Radar enabled the Wellingtons to find track and automatically bomb the targets.

    Wellingtons were also used by the 2nd Tactical Airforce as night reccon/strike aircraft close behind the German front lines, normally a maximum of 20 miles behind the lines. These didn't carry Radar but to help detect ground movement the front turret was removed and replaced with clear perspex. Initially they only took photo's but started carrying 250lb bombs.
     
  18. brickhistory

    brickhistory Member

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    jd,

    Try "AWACS and Hawkeyes" by Edwin Leigh Armistead, MBI Publishing, ISBN 0-7603-1140-4.

    Good history of AEW including the early work starting with a joint BuAir-BuShips Project NA-178 which led to Project Cadillac which led to AMTI, then the APS-20 in a TBM-3W, later B-17Gs in Navy colors called PB-1Ws.

    See also:
    DEVELOPMENT TO COMBAT: Additional Technological Developments

    which states the AN/APS-27 was developed in 1951:

    which would make sense as the nomenclature -20 vs. -27 would usually, but not always admittedly, chronologically organized.
     
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