SMILS.
Photo courtesy of Tom Graves. Posted Feb. 2014
From Left to right, Jerry Bell, Kevin Laudadio and Tom Graves, in flight suits aboard a P3 Orion aircraft, at the start of a mission.
What are 3 oceanographers doing up in the sky, when it would seem they should more likely be found in a submarine, or on board a ship, at least?
Answer: The SMILS Project!
SMILS is a three letter abbreviation for Sonobuoy Missile Impact Location System.
Sonobuoys are hydrophones that float at the surface of the ocean, and can record sounds within a close range of their location. They can also send out an underwater sound (a ping - see glossary) which can be heard by transponders that are located nearby on the ocean floor, and whose locations are accurately known. When a transponder hears a ping, it sends back a reply, which the sonobuoy can hear. Based on the time delays of the replies from several transponders, an accurate location of the sonobuoy can be determined. Sonobuoys can also hear the splash of a missile hitting the ocean nearby. (This is a much less dangerous practice than using the Sir Horace Lamb to record the splash - see 'Big Gun' under 'Projects'.) Based on the arrival time of the splash at several sonobuoys scattered around the supposed impact point of the missile, the exact point of impact, and hence the accuracy of the missile, can be calculated.
SOFAR had a P3 Orion aircraft assigned to it, fitted out with all the equipment necessary to record the necessary information.
What are 3 oceanographers doing up in the sky, when it would seem they should more likely be found in a submarine, or on board a ship, at least?
Answer: The SMILS Project!
SMILS is a three letter abbreviation for Sonobuoy Missile Impact Location System.
Sonobuoys are hydrophones that float at the surface of the ocean, and can record sounds within a close range of their location. They can also send out an underwater sound (a ping - see glossary) which can be heard by transponders that are located nearby on the ocean floor, and whose locations are accurately known. When a transponder hears a ping, it sends back a reply, which the sonobuoy can hear. Based on the time delays of the replies from several transponders, an accurate location of the sonobuoy can be determined. Sonobuoys can also hear the splash of a missile hitting the ocean nearby. (This is a much less dangerous practice than using the Sir Horace Lamb to record the splash - see 'Big Gun' under 'Projects'.) Based on the arrival time of the splash at several sonobuoys scattered around the supposed impact point of the missile, the exact point of impact, and hence the accuracy of the missile, can be calculated.
SOFAR had a P3 Orion aircraft assigned to it, fitted out with all the equipment necessary to record the necessary information.
The SOFAR VX-1 P3C Orion on the left. Photo courtesy of Mark Morrison. Photo taken 1977. Posted Feb. 2014
The SMILS Project was used for testing of the later Poseidon missiles, and also the Trident missiles. By this time, 'MIRV' had been invented. MIRV stands for Multiple Independently targetable Re-entry Vehicles. What this means is that one missile contains several warheads, that split off as the missile descends out of the sky, and each warhead travels to its intended target. This meant that there were several 'splashes' to be heard, and several sonobuoys needed to be placed in the ocean around each of the intended target areas.
{There was at least one attempt to use the former MILS system to determine the accuracy of MIRV impacts, which, while successful, was prone to error. For the first test, the intended target positions were known to the Data Analysts, who were able to untangle the multitude of almost simultaneous SOFAR bomb signal arrivals at the various hydrophones scattered around the Atlantic, and arrive at impact locations for each warhead (there were 12, as I recall), and hence give accuracy figures for the test. Had the intended target points not be known, the analysis would have been considerably more difficult, perhaps even impossible.}
There is a very interesting passage in a book, written by a former US Navy pilot, Bill Goss, about his experience piloting the P3C. I cannot print the passage here, because of copyright restrictions, but here is a link to the relevant pages, or copy the link below to your browser:-
http://books.google.co.cr/books?id=iU40bEkwtsEC&pg=PA103&lpg=PA103&dq=SMILS+Sonobuoy+Unlucky&source=bl&ots=ez773QJomG&sig=PFyvm-9d1f937bb6gGXzbePVzx4&hl=en&sa=X&ei=jg4MU8W_GcbokAeaooD4Cg&redir_esc=y#v=onepage&q=SMILS%20Sonobuoy%20Unlucky&f=false
If you then scroll down through 21pages of pictures, (Mr. Goss had quite an interesting life!) you will come to a very dramatic photo taken from the cockpit of the P3C.
Posted Feb. 2014
{There was at least one attempt to use the former MILS system to determine the accuracy of MIRV impacts, which, while successful, was prone to error. For the first test, the intended target positions were known to the Data Analysts, who were able to untangle the multitude of almost simultaneous SOFAR bomb signal arrivals at the various hydrophones scattered around the Atlantic, and arrive at impact locations for each warhead (there were 12, as I recall), and hence give accuracy figures for the test. Had the intended target points not be known, the analysis would have been considerably more difficult, perhaps even impossible.}
There is a very interesting passage in a book, written by a former US Navy pilot, Bill Goss, about his experience piloting the P3C. I cannot print the passage here, because of copyright restrictions, but here is a link to the relevant pages, or copy the link below to your browser:-
http://books.google.co.cr/books?id=iU40bEkwtsEC&pg=PA103&lpg=PA103&dq=SMILS+Sonobuoy+Unlucky&source=bl&ots=ez773QJomG&sig=PFyvm-9d1f937bb6gGXzbePVzx4&hl=en&sa=X&ei=jg4MU8W_GcbokAeaooD4Cg&redir_esc=y#v=onepage&q=SMILS%20Sonobuoy%20Unlucky&f=false
If you then scroll down through 21pages of pictures, (Mr. Goss had quite an interesting life!) you will come to a very dramatic photo taken from the cockpit of the P3C.
Posted Feb. 2014
Tom Graves & Tom Krantz aboard the P3C analyzing the results of the mission. I guess there was no A/C on this A/C!! ~~ Photo courtesy of Tom Graves.
Posted Feb. 2014
How SMILS worked!!
MILS diagram notes.
From the bottom of the page to the top.
DOT (does not mean Dept of Transport!) - Deep Ocean Transponder. (Perhaps there was a Shallow Ocean Transponder also!!) There would be more than 3 DOTs. Each Sonobuoy would need at least 3 well-placed DOTs to accurately locate itself.
For best results, 4 sonobuoys were needed, spread around the target area, to accurately locate the splash. Minimum 3 x 4 = 12 DOTs needed.
I don’t know whether 2 sonobuoys could ‘share’ a DOT that was close to both of them.
There were active and passive sonobuoys. Active sonobuoys would send out a unique underwater sound signal that would alert nearby sonobuoys to 1) send a time signal to the P-3, and to expect a signal from one or more transponders, and 2) receive that signal from the transponders and transmit it to the P3. Based on this information, the P-3 could accurately determine the exact location of each sonobuoy relative to the known location of the DOTs. This process was repeated at intervals of 1 minute during the test. When the splash occurred, the sonobuoys would transmit the time of arrival to the P-3. Each sonobuoy had a unique identifier that was transmitted with each message, to avoid any confusion! I believe that each transponder was programmed to send a unique response to the active sonobuoy’s signal.
From the bottom of the page to the top.
DOT (does not mean Dept of Transport!) - Deep Ocean Transponder. (Perhaps there was a Shallow Ocean Transponder also!!) There would be more than 3 DOTs. Each Sonobuoy would need at least 3 well-placed DOTs to accurately locate itself.
For best results, 4 sonobuoys were needed, spread around the target area, to accurately locate the splash. Minimum 3 x 4 = 12 DOTs needed.
I don’t know whether 2 sonobuoys could ‘share’ a DOT that was close to both of them.
There were active and passive sonobuoys. Active sonobuoys would send out a unique underwater sound signal that would alert nearby sonobuoys to 1) send a time signal to the P-3, and to expect a signal from one or more transponders, and 2) receive that signal from the transponders and transmit it to the P3. Based on this information, the P-3 could accurately determine the exact location of each sonobuoy relative to the known location of the DOTs. This process was repeated at intervals of 1 minute during the test. When the splash occurred, the sonobuoys would transmit the time of arrival to the P-3. Each sonobuoy had a unique identifier that was transmitted with each message, to avoid any confusion! I believe that each transponder was programmed to send a unique response to the active sonobuoy’s signal.
Posted Oct. 2020.