Satellite signals intelligence in the 1970s-1990s

[Blackstar]

Darn, they had to do this on the one day that I get really busy...

I guess this tease was a little more significant than some others

Yeah, although once my group broke for lunch from our task of saving planet Earth, I was able to read the press release and saw that they did not actually release much. We already knew the name, we also already knew what the satellites looked like. And as Jonathan McDowell can attest, we also had the numbers and the launch dates. So all they have done is confirm what was known, not provided any additional information that I can see. We'll still have to wait for that.

Also, I think that artwork and model do not depict the early satellite, but a later iteration. Compare it to previously released materials.

There was a graphic showing NRL satellites over several decades that I am pretty sure showed this spacecraft design before. I don't know what date that was or how they labeled it, but the graphic has been on the internet for a few decades now. We'll dig it up without too much trying.


Update: found it.

[LittleBird]

MSD with four sub sats ?

Darn, they had to do this on the one day that I get really busy...

I guess this tease was a little more significant than some others

Yeah, although once my group broke for lunch from our task of saving planet Earth, I was able to read the press release and saw that they did not actually release much. We already knew the name, we also already knew what the satellites looked like. And as Jonathan McDowell can attest, we also had the numbers and the launch dates. So all they have done is confirm what was known, not provided any additional information that I can see. We'll still have to wait for that.

Also, I think that artwork and model do not depict the early satellite, but a later iteration. Compare it to previously released materials.

There was a graphic showing NRL satellites over several decades that I am pretty sure showed this spacecraft design before. I don't know what date that was or how they labeled it, but the graphic has been on the internet for a few decades now. We'll dig it up without too much trying.


Update: found it.

I'm sure I am not the only one who will be looking back at your past TSR articles here  https://www.thespacereview.com/article/4204/1, here https://www.thespacereview.com/article/4174/1 and here https://www.thespacereview.com/article/4239/1 to see what the newest info tells us.

I wonder if you could get the Bradburn SIGINT book re examined as there is surely redacted material in there on PARCAE  ?

Meanwhile I am curious about the last image in your post, as it shows 4 satellites not 3 ?

 
 

[Skyrocket]

Meanwhile I am curious about the last image in your post, as it shows 4 satellites not 3 ?

I guess this was a misinterpretation what the PARCAE launches looked like, which did leave four instead of three subsatellites in orbit.

It was later revealed, that the fourth payload were the LIPS satellites, which were the jettisonable plume shields of the the MSD deployer modified to carry some experiments.

https://space.skyrocket.de/doc_sdat/lips.htm

[LittleBird]

Darn, they had to do this on the one day that I get really busy...

I guess this tease was a little more significant than some others

Yeah, although once my group broke for lunch from our task of saving planet Earth, I was able to read the press release and saw that they did not actually release much. We already knew the name, we also already knew what the satellites looked like. And as Jonathan McDowell can attest, we also had the numbers and the launch dates. So all they have done is confirm what was known, not provided any additional information that I can see. We'll still have to wait for that.

Also, I think that artwork and model do not depict the early satellite, but a later iteration. Compare it to previously released materials.

There was a graphic showing NRL satellites over several decades that I am pretty sure showed this spacecraft design before. I don't know what date that was or how they labeled it, but the graphic has been on the internet for a few decades now. We'll dig it up without too much trying.


Update: found it.

<snip>

Meanwhile I am curious about the last image in your post, as it shows 4 satellites not 3 ?

Thanks for your reply Skyrocket, and I see this image has been discussed before, in the interesting Atlas variants thread: https://forum.nasaspaceflight.com/index.php?topic=26915.msg1403540#msg1403540

You may well be right that it was a misinterpretation but do we have any idea at all when it dates from, and who drew it-was it FAS or an official image ? The link to FAS no longer works and iirc Blackstar said he received it from a FOIA request.

And would the change from Atlas F to H have allowed enough extra payload for a fourth sub satellite ?

[Blackstar]

I guess this was a misinterpretation what the PARCAE launches looked like, which did leave four instead of three subsatellites in orbit.

I obtained that image from NRL. So they produced it.

[LittleBird]

COMINT on Improved PARCAE: satellites or bus ?


Splitting this off as a separate topic.

I am also curious about the COMINT role of the Improved PARCAE, which I would have thought would be better done by its Titan launch dispenser after that was boosted into a HEO orbit. Notably we know it was also used for the SLDCOM satcom role https://space.skyrocket.de/doc_sdat/sldcom.htm . Was the TLD perhaps what they meant ?

[LittleBird]

I wonder if NRL will be adding anything on their pages and/or doing any events ?

NRL news release from Friday:

NEWS | Sept. 29, 2023
America’s Ears in Space: NRO Declassified NRL-Developed Electronic Intelligence Satellite Program

By Nicholas Pasquini, U.S. Naval Research Laboratory Corporate Communications

ARLINGTON, Va.  –   During a Centennial Exhibition, held at the Pentagon on Sept. 28, to commemorate the U.S. Naval Research Laboratory’s (NRL) 100 years of operations, the National Reconnaissance Office (NRO) declassified an NRL-developed electronic intelligence satellite program called Parcae.

“With 100 years of history, the Naval Research Lab has been advancing science in national security well before we could actually leverage space,” said Dr. Troy Meink, principal deputy director of the NRO. “Today’s Centennial offers an opportunity to talk about how the lab’s many innovations have helped the National Reconnaissance Office use the vantage point of space to keep America safe and stronger.”

Launched from 1976 to 1996, under mission numbers 7108 and 7120, Parcae and Improved Parcae were Low Earth Orbit electronic intelligence collection systems that downlinked the collected data to ground processing facilities located at selected locations around the world. Once received, the data was provided to the National Security Agency for processing and reporting to U.S. policymakers.

After the success of the GRAB and Poppy signals collection programs, and with increasing concerns about the Soviet Navy, NRL, as part of the NRO’s Program C, developed the next system that would collect the needed information on the Soviet Union’s naval fleet. The system, Parcae, was the programmatic follow-on to GRAB and Poppy.

Later on, the NRO developed the next generation of Parcae, referred to as Improved Parcae, which added the capability to collect against and recognize selected foreign communication systems.

“What we are celebrating today, is not simply the journey of the Navy’s premiere research laboratory or its contributions to the naval service, instead we are celebrating a journey of American ingenuity and a legacy of our best scientists,” said Under Secretary of the Navy the Honorable Erik K. Raven and presiding host. “Our ability to deal with national security and economic threats of today rests heavily on the work of the scientists, engineers and support staff at the Naval Research Laboratory.”
 
For the first time, a model of Parcae was on display during the exhibition. The NRL workforce showcased their past, present, and future research and highlighted the enduring relationship with government partners and the need for continued investment in scientific research.

“With our eyes fixed on the future, NRL’s first century must inspire resilience in us as serious threats remain,” said Dr. Bruce Danly, NRL director of research. “The NRL ventures now into its next century with the same strong commitment to a vital mission that cannot rest.”
 
Since opening its gates in 1923, NRL has changed warfighter technologies, advanced military capabilities, surpassed contemporary scientific understanding, and transferred vital innovations to industry.
 
“We are indeed in an innovative race and it is one that we must win – innovation must always permeate every aspect of our Department’s approach to the delivery of technologies and capabilities at the speed and scale necessary for our Navy and Marine Corps to be successful,” said Secretary of the Navy the Honorable Carlos Del Toro. “I encourage all of you, our nation’s scientists, engineers, researcher, inventors, entrepreneurs and problem solvers to join us.”
 
 
About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the U.S. Navy and Marine Corps from the seafloor to space and in the information domain. NRL is located in Washington, D.C. with major field sites in Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers and support personnel.

For more information, contact NRL Corporate Communications at (202) 480-3746 or [email protected].

[Blackstar]

So this still leaves us with a mystery until we get further information. How come the artwork (and model) released by NRO doesn't look like the very first artwork leaked to Aviation Week, or the photo posted above? How come it looks like the 180/190 satellites in this illustration?

One possibility is that they went through several iterations, a pyramidal shape, a box shape, and then whatever we got with the "improved" version.

The press releases were really devoid of much information, but I'll stop gritting my teeth because I do think there's a good chance we'll get documents and maybe an official history out of this. And we can probably go ahead and FOIA the relevant section of The SIGINT Satellite Story now.

It's worth revisiting my article from June 2021:

https://thespacereview.com/article/4204/1

"Whereas the early years of the PARCAE satellites appear to have been intended to give the US Navy the ability to track Soviet warships on the open ocean, by the 1980s, the goal became to use the satellites to enable the Navy to directly target ships with weapons. In the 2010 book From the Sea to the Stars: A Chronicle of the U.S. Navy's Space and Space-related Activities, 1944-2009, the authors describe how the US Navy in the early 1980s sought to integrate satellites directly into their warfighting. According to the book, the Naval Ocean Surveillance Information Center (NOSIC), located at Suitland, Maryland, gathered and correlated intelligence information from all sources that would be useful to the fleet. Shore-based Fleet Ocean Surveillance Information Centers or Facilities—like the one on Treasure Island used for Project TANGIBLE in 1971—were in each theater where naval forces operated. Information collected at these locations was then transmitted as classified messages to submarines, surface ships, and aircraft.

By 1983, the US Navy was facing a dilemma because its Harpoon and Tomahawk anti-ship missiles could reach beyond the sensor range of their launching ships. At the time, the PARCAE satellites were providing data to Regional Reporting Centers, which then sent it to ships at sea as messages known as SELORs, for Ships Emitter Locating Reports.

Although the details remain classified, the Navy soon adopted a new approach called the “sensor-to-shooter” concept. Instead of the PARCAE satellite data being sent to the RRCs and then to the ships, the information would be made automatically available to the weapons control stations in ships, subs, and aircraft. Navy ships and aircraft were already exchanging tactical data in near realtime. This approach meant that more data could be delivered in useable form. The data would also go to the intelligence nodes on land to be combined with other intelligence data.

This new concept required that the satellite systems collect, process, and automatically report the information. The initial plan was that space-based radar would be an additional component, but this was never developed.

This new approach required direct communications from the satellites to the ships and aircraft. This was implemented as the Tactical Data Information Exchange System-Broadcast (TADIXS-B). It was later replaced by the Tactical Receive Equipment (TRE) and Related Applications (TRAP) Broadcast. Eventually this evolved into the Integrated Broadcast Service Simplex (IBS-S). At some point the Navy developed the requirement for no more than a two-minute delay from time of observation to reporting to tactical users for early warning and targeting support—compared to the several hours it took to report the information a decade earlier. It is unclear how they achieved this impressive feat, but it apparently became the norm for the ocean surveillance system."

[Blackstar]

Well shiver me timbers and call me a pirate. Look at the images. They're different satellites.

[Skyrocket]

Well shiver me timbers and call me a pirate. Look at the images. They're different satellites.

As only the the first two PARCAE missions were built by NRL and the later 1st generation PARCAE were built by Martin Marietta, this may explain the difference. The model satellite pretty much matches the photograph of the cluster "released" earlier.

But I suspect that the illustration on the left is just an early artist impression with less details then the finished satellite, while the model matches the real satellite.

I do not think the model shows the 2nd generation improved PARCAE.

[LittleBird]

Well shiver me timbers and call me a pirate. Look at the images. They're different satellites.

As only the the first two PARCAE missions were built by NRL and the later 1st generation PARCAE were built by Martin Marietta, this may explain the difference. The model satellite pretty much matches the photograph of the cluster "released" earlier.

Indeed. Model also seems to match the subsats in the AW&ST image from 1976, as per grab below.

But I suspect that the illustration on the left is just an early artist impression with less details then the finished satellite, while the model matches the real satellite.

I do not think the model shows the 2nd generation improved PARCAE.

Which I don't think we've seen yet, right ? Except maybe in a picture of the TLD in a Navy history from a few years ago ? [Edit: Turns out to be a no, not a maybe, in that case. History I was thinking of was Amato and I don't think that shows a TLD photo, just a partially visble MSD without its satellites.]

[LittleBird]

So this still leaves us with a mystery until we get further information. How come the artwork (and model) released by NRO doesn't look like the very first artwork leaked to Aviation Week, or the photo posted above? How come it looks like the 180/190 satellites in this illustration?

One possibility is that they went through several iterations, a pyramidal shape, a box shape, and then whatever we got with the "improved" version.

The press releases were really devoid of much information, but I'll stop gritting my teeth because I do think there's a good chance we'll get documents and maybe an official history out of this. And we can probably go ahead and FOIA the relevant section of The SIGINT Satellite Story now.

It's worth revisiting my article from June 2021:

https://thespacereview.com/article/4204/1


"Whereas the early years of the PARCAE satellites appear to have been intended to give the US Navy the ability to track Soviet warships on the open ocean, by the 1980s, the goal became to use the satellites to enable the Navy to directly target ships with weapons. In the 2010 book From the Sea to the Stars: A Chronicle of the U.S. Navy's Space and Space-related Activities, 1944-2009, the authors describe how the US Navy in the early 1980s sought to integrate satellites directly into their warfighting. According to the book, the Naval Ocean Surveillance Information Center (NOSIC), located at Suitland, Maryland, gathered and correlated intelligence information from all sources that would be useful to the fleet. Shore-based Fleet Ocean Surveillance Information Centers or Facilities—like the one on Treasure Island used for Project TANGIBLE in 1971—were in each theater where naval forces operated. Information collected at these locations was then transmitted as classified messages to submarines, surface ships, and aircraft.

By 1983, the US Navy was facing a dilemma because its Harpoon and Tomahawk anti-ship missiles could reach beyond the sensor range of their launching ships. At the time, the PARCAE satellites were providing data to Regional Reporting Centers, which then sent it to ships at sea as messages known as SELORs, for Ships Emitter Locating Reports.

Although the details remain classified, the Navy soon adopted a new approach called the “sensor-to-shooter” concept. Instead of the PARCAE satellite data being sent to the RRCs and then to the ships, the information would be made automatically available to the weapons control stations in ships, subs, and aircraft. Navy ships and aircraft were already exchanging tactical data in near realtime. This approach meant that more data could be delivered in useable form. The data would also go to the intelligence nodes on land to be combined with other intelligence data.

This new concept required that the satellite systems collect, process, and automatically report the information. The initial plan was that space-based radar would be an additional component, but this was never developed.

This new approach required direct communications from the satellites to the ships and aircraft. This was implemented as the Tactical Data Information Exchange System-Broadcast (TADIXS-B). It was later replaced by the Tactical Receive Equipment (TRE) and Related Applications (TRAP) Broadcast. Eventually this evolved into the Integrated Broadcast Service Simplex (IBS-S). At some point the Navy developed the requirement for no more than a two-minute delay from time of observation to reporting to tactical users for early warning and targeting support—compared to the several hours it took to report the information a decade earlier. It is unclear how they achieved this impressive feat, but it apparently became the norm for the ocean surveillance system."

It's always worth revisiting your articles, and in this case it is worth comparing with the Amato history "Taking Technology Higher" that came out a bit later https://www.nrl.navy.mil/Our-Work/Areas-of-Research/Naval-Center-for-Space-Technology/ and which explains how the LIPS system mentioned upthread by Guenter was mainly for comms, and was the first step in this process, see grabs below and following pages which tell story up to TADIXS-B.

So there was a kind of block change in the initial Atlas launched PARCAEs, i.e. before LIPS and after. [Edit: As far as I can see this corresponds to the change from SSU 1 to SSU 1A in the terminology of Andronov in 1993, see  https://www.globalsecurity.org/space/library/report/1993/noss_andronov.htm]

[Blackstar]

Previously we sometimes had good explanations for the names of satellite systems and sometimes we had to guess. PARCAE is actually rather obvious. The name derives from Roman mythology, where the Parcae determined the fate of mortals. The NRL satellites could determine the fate of ships during wartime. There were three Parcae, and their particular skills may have been directly related to what the satellites did.

[LittleBird]

Previously we sometimes had good explanations for the names of satellite systems and sometimes we had to guess. PARCAE is actually rather obvious. The name derives from Roman mythology, where the Parcae determined the fate of mortals. The NRL satellites could determine the fate of ships during wartime. There were three Parcae, and their particular skills may have been directly related to what the satellites did.

Out of interest, can you remember when this was first spelled out ? Oldest place I can recall is in Andronov's article, translated from the Russian by Allen Thomson, in 1993: https://www.globalsecurity.org/space/library/report/1993/noss_andronov.htm

The mythological Parcae were the three daughters of Zeus and the goddess Themida (the SSU satellites are launched in groups of three and fly relatively close together.) One of the daughters spins the thread of fate for each mortal (one satellite has a wide observation swath, but cannot exactly determine the coordinates of radio emitters). The second daughter measures out a length of thread for each person (when two satellites get a fix on the shipborne emitters, the position is obtained, but with some ambiguity). The third sister (Atropos - "she from whom one may not flee") cuts the measured thread of life (the third satellite, getting a fix on the emitters' signals, enables their coordinates to be determined precisely and then transmitted to Navy ships for weapons employment.

Andronov's description of how they worked sounds plausible to me, but I am not an RF expert:

Calculations indicate that in order to compute the direction and speed of ships using one group of satellites it is necessary to have fixes with a precision of the order of 2 to 3 km, or 8 to 10 km if four satellites are used. The task of determining the bearings of naval targets is made easier by the fact that practically all ships have continually operating emitters fulfilling various purposes: communications, navigation, surface and air search, and weapons control.

For determining the bearings of signals from different directions using the method of time difference of arrival, the intersatellite baselines (the imaginary straight line segments connecting the satellites) should form a right angle (or, at least, not be parallel). These conditions are fulfilled through the orbital parameters chosen for the satellites. As a group flies over the equator the baselines form a figure which is close to a right triangle (Fig. 2). However, in the polar regions, as the satellites go through latitudes which correspond to the maximum inclination of their orbits (around 63 deg.), the form of the group changes, and the satellites follow practically along one and the same trajectory one after the other. In order to avoid decreased signal bearing accuracy, the apogee portion of the orbit of one of the satellites is shifted relative to the apogee portions of the others. Thanks to this, in the polar regions one of the satellites moves 50 to 100 km lower [sic; this doesn't seem to agree with Figures 2 and 3] than the remaining ones, which lets the direction-finding baselines spread out and eliminates the "zone of inaccessability." (Fig. 3)

NB the figures from the original are not on the FAS site. My non expert impression is that this article was more accurate than Andronov's contemporary piece on GEO SIGINT, which afaik was where the name CANYON first surfaced.

[Blackstar]

Out of interest, can you remember when this was first spelled out ? Oldest place I can recall is in Andronov's article, translated from the Russian by Allen Thomson, in 1993: https://www.globalsecurity.org/space/library/report/1993/noss_andronov.htm

I think it is in one of Richelson's books. Maybe the 1990 one, if not the earlier US Intelligence Community books.

[LittleBird]

Out of interest, can you remember when this was first spelled out ? Oldest place I can recall is in Andronov's article, translated from the Russian by Allen Thomson, in 1993: https://www.globalsecurity.org/space/library/report/1993/noss_andronov.htm

I think it is in one of Richelson's books. Maybe the 1990 one, if not the earlier US Intelligence Community books.

Interestingly the copy I have, the 1995 3rd edition, has the PARCAE name and cites Andronov but actually doesn't have the explanation. I'll have a look at some of the other versions on archive.org at some point.

[Blackstar]

Out of interest, can you remember when this was first spelled out ? Oldest place I can recall is in Andronov's article, translated from the Russian by Allen Thomson, in 1993: https://www.globalsecurity.org/space/library/report/1993/noss_andronov.htm

I think it is in one of Richelson's books. Maybe the 1990 one, if not the earlier US Intelligence Community books.

Interestingly the copy I have, the 1995 3rd edition, has the PARCAE name and cites Andronov but actually doesn't have the explanation. I'll have a look at some of the other versions on archive.org at some point.

I have the 3rd edition but did not see it in there. I also have the 7th edition (2016), which cites Andronov. I looked in "Secret Eyes in Space" (1990) and did not see it there in the index, not even as "White Cloud."

[Targeteer]

Previously we sometimes had good explanations for the names of satellite systems and sometimes we had to guess. PARCAE is actually rather obvious. The name derives from Roman mythology, where the Parcae determined the fate of mortals. The NRL satellites could determine the fate of ships during wartime. There were three Parcae, and their particular skills may have been directly related to what the satellites did.

The focus of the now officially revealed PARCAE on ship detection has always confused and frustrated me.  It's NRL roots obviously point to ship emissions detection being a focus, but having dealt with the receipt and use of it's data with deployable systems while in an Air Force F-16 unit, as I've described previously https://www.globalsecurity.org/intell/systems/constant_source.htm , I think the ship detection functionality/relevance is over stated.  Frankly, non threat data clogged the real time feeds and required careful filtering to avoid crashing the processing systems.  Use of the data by flying units of all services to update baseline SAM threat order of battle in near real time, as described in the link above, was far more useful and relevant, in my humble opinion. We did it during Southern Watch.  Looking forward to further releases so discussions can occur without a visit from the FBI

[Blackstar]

The focus of the now officially revealed PARCAE on ship detection has always confused and frustrated me.  It's NRL roots obviously point to ship emissions detection being a focus, but having dealt with the receipt and use of it's data with

SNIP

more useful and relevant, in my humble opinion. We did it during Southern Watch.  Looking forward to further releases so discussions can occur without a visit from the FBI

I think part of the issue is going to be what/when. It clearly started as an ocean surveillance system in 1976. What it evolved into is another question. I'm hoping that we get a decent official history, but I've found the histories of SIGINT systems to be rather spotty.

(Sidenote: Tooting my own horn a bit here, but when I've researched and written about photo-reconnaissance satellites, there were already pretty good official histories of those programs that people can read. When it comes to the SIGINT stuff, they're a lot messier. It appears that they are not as well written, plus they have more random redactions.)

[LittleBird]

Edited after the 2024 declassifications to reflect the newer info:

The focus of the now officially revealed PARCAE on ship detection has always confused and frustrated me.  It's NRL roots obviously point to ship emissions detection being a focus, but having dealt with the receipt and use of it's data with

SNIP

more useful and relevant, in my humble opinion. We did it during Southern Watch.  Looking forward to further releases so discussions can occur without a visit from the FBI

I think part of the issue is going to be what/when. It clearly started as an ocean surveillance system in 1976. What it evolved into is another question. I'm hoping that we get a decent official history, but I've found the histories of SIGINT systems to be rather spotty.

I think a key thing to bear in mind is going to be that Poppy and its successors were real time. That was a crucial difference between them and the 989s etc, irrespective of whether mission was Naval or not, and is stressed even in the unredacted conclusions of Bradburn et al for example.

My impression is that Bradburn history was written for the particpiants' benefit more than for posterity, and possibly for ease of partial declassification.

(Sidenote: Tooting my own horn a bit here, but when I've researched and written about photo-reconnaissance satellites, there were already pretty good official histories of those programs that people can read. When it comes to the SIGINT stuff, they're a lot messier. It appears that they are not as well written, plus they have more random redactions.)

I understand these frustrations but I still think to get the best out of Bradburn, and maybe even to target FOIAs better, one needs  to look at how it is laid out.

It appears to follow the (TK) 7xxx mission numbering scheme for chapters 3, 4 and 5

 
Mission 710x, 711x & 712x (Bradburn Chapter 3) Navy NRO Program C: 7101 to 8  are the POPPYs. Last part of that chapter, pp 68-75 is redacted. As we now know PARCAE followed on as  the 711x and 712x series I'd guess it is indeed about the Atlas F launched early PARCAEs. Main counter argument to that is that there is no deleted pic for that section. They may have started the PARCAE material here and then taken the story up in a late chapter ?

Mission 715x and 716x (Chapter 4) AF NRO Program A free flyers: 715x are the main WS117L Agena derived payloads and run  from 7151 in 1962 to the last flown STRAWMAN/THRESHER, 7167 (?).

Mission 72xx and 73xx (Chapter 5) AF NRO Program A hosted payloads and subsats: 72xx goes from 1962 to 66 and covers AFTRACK first. Bradburn notes that 72xx goes on to other secondary payloads,  certainly some of the payloads hosted on MULTIGROUP and STRAWMAN up to 1970, the latter ending with HARVESTER/7240 in 1971.  The LORRI hosted payloads on HEXAGON were also in this series, after book's 1975 cutoff date.   

Chapter 5 continues with 73xx which goes from 1963 to 1975 for P-11s.  73xx mission numbers  continued to be used for later 989 missions  including  the Titan II spinners.   

If there was a mission 74xx one guesses it would need to be somewhere in Bradburn. It would logically have debuted before there was a need for the TK access to CANYON (mission 7500) output. This gives a time frame of, at the latest, somewhere between CANYON 1 (which may not have given usable data) in mid 1968 and CANYON 2 in 1969 .

Book appears to then switch to the order in which the programs were started and so breaks the 7xxx sequence. It may be  organising chapters by satellites' initial primary role, or simply just breaking up the topics to make giving a snapshot of the system in 1975 as easy as possible.

Mission 76xx  (Chapter 6) Program B TELINT ? Started earlier but flown later, 76xx runs from first RHYOLITE to last of its line, reportedly merged into 8300 IOSA GEO payloads in the 21st Century. The book presumably just deals with the Atlas Agena payloads up to 1978. Chapter contents clear enough from its first page.

Mission 75xx (Chapter 7) Program A COMINT ? Again reportedly the 75xx numbering  runs all the way from  first CANYON in 68 to the last COMINT GEO mission (the failed 7516) before the merged 8300 series. The book would cover the earliest Atlas Agena family and maybe the Titan IIIC versions. COMINT relevance pretty clear from the only unredacted section, last grab, about NSA hiring foreign language speakers.

Mission 77xx ?  (Chapter 8 ) Program A's JUMPSEAT and hunting ABMs ? Seems most likely this was about hunting the ABM, and thus in particular Program A's  JUMPSEAT.  I can't recall if JUMPSEAT was rumoured to have a 7xxx number but 77xx would be logical here it appears even from the heavily redacted account in the other main source, Butterworth, to have started after the 75/76xx programmes, and it made its orbital debut after them. The chapter has a picture of Davis in it, whose committee played a key role in the ABM search ramp up.

An alternative  theme would be the increasing use of NRO data by military customers. As the book had a cutoff of mid 70s it was a bit too early for much of this story, but we are learning nowadays much more about surprisingly early developments, such as the use of P-11 during 1973's October war.

 
Mission 78xx, the interference detection system which has recently been mentioned in a new document and which succeeded the original 70xx Bit Boxes is not covered, or at least not given a whole chapter. It was not a SIGINT system per se, and may well not have been in the book.