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Gemini-7: Lessons and Legends (A 30th Anniversary Revisit

"Formation Flying", "Lessons Learned" Later, and one "Bogey"

James Oberg // September 15, 1995

Copyright 1995 James Oberg.

One of the central purposes of the Gemini program in 1965-1966 was to perfect the techniques of orbital rendezvous and docking, since the Apollo program would rely on the "Lunar Orbit Rendezvous" strategy to beat the Russians to the Moon (as it turns out, the Russians also chose that strategy). This purpose was completely fulfilled by the end of 1966, but in so doing, some of the early steps got forgotten in the rush to proceed to the more complex steps.

The Gemini-7 mission in December 1965 achieved some remarkable "firsts" in the area of manned "formation flying" (in NASA terminology, "stationkeeping") and relative maneuvering in orbit (what NASA calls "proximity operations", or "prox ops"), and although these were soon eclipsed by more sophisticated accomplishments, a new analysis of the Gemini-7 events can provide important lessons that are relevant even today. Complete reconstruction of the relative trajectory was not done at the time due to schedule pressure (all the specialists were fully committed to subsequent flight activities) which precluded paying attention to recording history. But now has been done by me and subsequently verified by the flight crew, and this has purely historical value as well.

The absence of a reliable trajectory analysis of the Gemini-7 mission also had the unintended and humorous by-product of allowing some of the astronauts' comments during the formation flying to be misunderstood and misinterpreted by some elements of the public to be references, not to elements of their own mission, but to some sort of "unidentified flying object", a "true UFO". When compared to what is now known about the trajectory, that mis-impression can be cleared up, but the way in which the story started, spread, and metastasized into new forms is an amusing sideshow of spaceflight history all its own

Trajectory Analysis

As part of the historical "knowledge capture" efforts for documenting "lessons learned" in orbital flight design, for the NASA data base, I wrote up the following trajectory reconstruction in December 1993. But as later sections show, this has much wider interest than just for trajectory experts.

Following the failure of Gemini-4 to accomplish a planned return and stable stationkeeping with its Titan-2 second stage in June 1965, the next rendezvous relevant historical event in most people's minds is the Gemini-6/Gemini-7 rendezvous the following December 15 ("Mission 76"). However, Gemini-7 also carried out another significant rendezvous-related feat that has been forgotten: following its own launch at 2:30 PM EST on December 4, it successfully carried out the task originally assigned to Gemini-4, first by returning to the vicinity of the booster and maintaining a controlled relative position, and then by performing the first "breakout" orbital separation burn to terminate stationkeeping.

Gemini-7 was launched from Cape Kennedy Launch Complex 19 on a launch azimuth of 083.6 degrees into an orbit with an inclination of 28.87 degrees. Insertion occurred at MET 05:37 with a velocity of 25,796 ft/sec, a 12 ft/sec underspeed (no problem), with the initial orbit of 87.2 by 177.1 NM (planned 87 - 183) and a period of 88.4 min. Command pilot Borman manually performed a 2 ft/sec posigrade separation burn from the Titan-2 stage (all previous Gemini flights also performed this separation manually). This moved him ahead of the booster along its orbital path (the positive velocity vector, or +VBAR). He then began the "stationkeeping" (NASA's term for formation flying) exercise.


The "Formation Flying": Borman yawed the Gemini spacecraft 180 degrees (at about 3-4 degrees per sec) and faced the upper stage, which was venting strongly ("There it was, bigger than the devil", he recalled). There was also scattered small debris in sight between them and the booster. He had probably pulled only 200 feet ahead of the stage (Aviation Week incorrectly wrote "about 1 mi."). Borman performed another set of +X pulses (about 6 ft/sec in total) to approach the stage, and then took up position about 50-60 ft directly ahead of it. He later reported that this quick out-and- back procedure "solves the problem" (the one that had frustrated McDivitt six months earlier) because it "takes a lot of the orbital mechanics out of the situation".

During this time, as they were flying eastwards across the North Atlantic, the crew was viewing the booster looking back westwards toward the setting sun, which made observing it "a little difficult". Reported Borman "The booster was right in line with the sun. It was just like flying formation when the leader makes a turn and you are down sun." As a result, he fired the Gemini's thruster to move off to one side, north of track, "where I could get the sun out of my line of sight". This small "out of plane" burn unintentionally started a pattern of criss-crossing paths with the booster and its debris cloud.

The Titan-2 upper stage had four tracking lights on it, which the crew was to evaluate for assisting their estimation of range. All these range estimates were done purely by eyeball, since Gemini-7 carried no radar. In any case, the generic Gemini radar operated only in transponder ("active") mode with a target vehicle. It could not do passive mode tracking ("skin track"). The Gemini also had a docking light which was aimed at the booster after sunset, but it "was not particularly helpful", probably because they were too far away (it later worked fine with Gemini-6 at a much closer range).

While Borman did the "formation flying" with the cast-off upper stage, co-pilot Lovell performed DoD experiment D-4/D-7 to take infrared readings of the spent stage with an small photometric instrument mounted on the side of the spacecraft. He also made a series of dramatic movie images showing white plumes spraying from the chaotically tumbling stage.

The crew several times commented on the violently tumbling and venting stage, and on how it appeared to be translating as well as rotating. This required more manual corrective rocket firings, which made controlled stationkeeping more propellant expensive but still not difficult. "A couple of times we got in a little too close and I backed out," Borman later reported, "because you just do not dare get as close as you do the way this thing is spewing." It was "definitely an order of magnitude more difficult than stationkeeping with a stable vehicle like [Gemini] 6," he continued, comparing it to maneuvers he flew eleven days later after the "76" rendezvous with Gemini-6, when they came to within a foot of each other.

As to using the lights for judging distance, Borman was not hopeful. "Jim McDivitt has made some comment about not being able to judge distance because they only had two lights on there", he later told debriefers. "We had four lights on and I'll be darned if I will try to judge distance by four lights, or by fifty lights. You have got to have illumination or you have to have a stable vehicle."

Borman continued stationkeeping for about 15 minutes, just a few minutes less than planned. Propellant expenditure ran about 7% over expected values.


The Separation Burn: The separation burn had originally been planned to occur about MET 00:25, about 5 minutes after sunset. It would push the Gemini down below the booster's flight path, where it would then pull ahead before rising back up to the flight path, then continue higher and fall back toward the booster, and then eventually circle back automatically to its original relative position once every full orbit of the Earth. This repeating trajectory is a consequence of laws of celestial mechanics as applied to two nearby-orbiting space objects.

Borman initiated the burn at MET 00:21:13 using Z axis ("up-down") jets, and burned for 20 seconds, resulting in an estimated delta-V of about 9 ft/sec. The Gemini spacecraft's attitude was supposed to have been pitch -25 degrees with zero yaw, but in flight was pitch -41.5 degrees, with a 49 degrees yaw error due to his out-of-plane detour to get the sun out of his eyes. This pitch error added a small unplanned posigrade component to the separation burn. The unplanned small out-of-plane component also remained in force.

This "equi-period" football-shaped trajectory was designed to allow extended photometric observation of the second stage against space and earth background. Recontact does not appear to have been a concern. The "football" would have been about five miles long with recurring close approaches every revolution (about every 90 minutes). Trajectory disturbance by differential drag (air drag affected the two vehicles differently because their mass-to-area ratios were different) and venting effects (the booster was being pushed in unexpected directions by leftover propellant streaming out its engine bell) could probably be counted on to preclude recontact, or so everybody had assumed.

At MET 0:43:00, while taking instrument readings of the booster, the crew saw it pass within two degrees of the moon.

As expected, the spacecraft returned to the vicinity of the booster about a rev later. At approximately MET 01:44:00 (80 minutes after the radial sep burn) the crew reported seeing the tumbling booster "surrounded by a billion particles" ahead of them. At the same time they also described encountering "hundreds of little particles" going by from the left, at an estimated range of "three to four miles", and in an presumably "polar orbit".

These "polar orbit" particles were evidently ice flakes from the second stage's spewed rocket propellant, in the expected "one rev return" football but probably with a small out-of-plane component as well. That component could have come from them being sprayed out to the side as the booster tumbled, or from the Gemini's own out-of-plane maneuver to avoid sun glare, or from a combination of both.

They could not actually have been in a genuine polar orbit, with an inclination of 80 or 90 degrees. Such true "polar orbit" satellites would have crossed the astronauts' field of view in seconds with a tremendous relative speed (several miles per second), so these particles are clearly from the booster.


Borman's "Bogey". A detailed transcripts of the crew's discussion later wound up, in all places, in the "Scientific Study of Unidentified Flying Objects", Dr. Edward Condon, project director, Bantam, 1969. Section 9 of chapter 6 (pp 176-209) was "Visual Observations Made by Astronauts", written by Dr. Franklin Roach. In a subsection entitled "Unidentified Flying Objects" (pp. 204-208), Dr. Roach wrote that "There are three visual sightings made by the astronauts while in orbit which, in the judgment of the writer, have not been adequately explained. These are: 1. Gemini-4. . . . 2. Gemini-4. . . . (and) 3. Gemini-7, astronaut Borman saw what he referred to as a 'bogey' flying in formation with the spacecraft. . . ."

"Portions of the transcript (GT 7/6, tape 51, pages 4,5,6) from Gemini 7 are reproduced here. The following conversation took place between the spacecraft and the ground control at Houston and referred to a sighting at the start of the second revolution of the flight.

Spacecraft: Gemini-7 here. Houston, how do you read?

Capcom: Loud and clear, Seven, go ahead.

Spacecraft: Bogey at 10 o'clock high.

Capcom: This is Houston. Say again, seven.

Spacecraft: Said we have a bogey at 10 o'clock high.

Capcom: Roger, Gemini 7, is that the booster or is that an actual sighting? Spacecraft: We have several, looks like debris up here. Actual sighting.

Capcom: You have any more information? Estimate distance and speed? Spacecraft: We also have the booster in sight.

Capcom: Understand you also have the booster in sight. Roger.

Spacecraft: Yeah, have a very, very many -- look like hundreds of little particles banked on the left out about 3 to 4 miles.

Capcom: Understand you have many small particles going by on the left. At what distance?

Spacecraft: Oh, about -- it looks like a path to the vehicle at 90 degrees.

Capcom: Roger, understand they are about 3 or 4 miles away.

Spacecraft: They are passed now -- they were in polar orbit.

Capcom: Roger, understand they are about 3 or 4 miles away.

Spacecraft: That's what it appeared like. That's roger.

Capcom: Were these particles in addition to the booster and the bogey at 10 o'clock?

Spacecraft: Roger

Spacecraft (Lovell): I have the booster on MY side, it's a brilliant body in the sun, against a black background with trillions of particles on it.

Capcom: Roger. What direction is it from you?

Spacecraft (Lovell): It's about at my 2 o'clock position.

Capcom: Does that mean it's ahead of you?

Spacecraft:. It's ahead of us at 2 o'clock, slowly tumbling.

Dr. Roach continued: "The general reconstruction of the sighting based on the above conversation is that in addition to the booster traveling in an orbit similar to the spacecraft there was another bright object (bogey) together with many illuminated particles. It might be conjectured that the bogey and the particles were fragments from the launching of Gemini 7, but this is impossible if they were traveling in polar orbit as they appeared to the astronauts to be doing" (but in that case it couldn't have been "in formation" with Gemini-7, as he had carelessly written). He concluded, "The... unexplained sightings which have been gleaned from a great mass of reports are a challenge to the analyst. . ."

Evidently, until this current trajectory reconstruction was undertaken, no analyst had accepted that "challenge"! But now that the repeating orbital pattern of the booster and its sky full of associated debris is understood, the objects seen by the crew, and the exact time they saw them, fall into place. The "bogey" was evidently just a brighter-than-average piece of booster-associated debris since it was in an orbit similar to the other booster-generated particles and fragments.


The Posigrade Burn: At MET 03:02:00 (about 80 more minutes later, after another full orbit of the Earth) the crew again reported spotting the booster ahead of them and somewhat below, "quite aways out", as it crossed the horizon. They did not watch it for long since they were preparing for a major perigee-raise burn, the biggest rocket firing since they had reached orbit.

At MET 3:48:00, a 59 ft/sec posigrade burn at apogee (lasting 76 seconds) raised the perigee from 87 NM to 120 NM. This was in preparation for the Gemini- 6 launch planned for eight days later. The burn was manually controlled by co- pilot Jim Lovell.

The burn was not performed as planned because of yet another re-encounter with booster- related debris during the burn. "We had come back into the vicinity of the booster", Borman later told debriefers. "Just about midway through the burn the booster venting that was still occurring suddenly lit up, became lit up. It looked like we were flying through a lot of foreign objects or debris. I was afraid we were going to hit something." Lovell cut off the burn a few seconds early.

At that point, a trailing strap attached to the rear of the spacecraft whipped forward and slapped across the right window, alarming and confusing the crew. "It made a noise and I thought we had hit some of the stuff that was spewing out of the booster," Borman recalled later. They saw from their delta-V display that they hadn't burned enough, so they pushed the hand controller for a few more seconds. They actually got very close to the planned delta-V for the burn.

This last report of booster/debris re-encounter can enable today's orbital mechanics analysts to estimate the actual relative motion of the Gemini and the second stage during these first three revs. Clearly the original flight design had expected that the "down football" relative motion maneuver, created by the initial downwards separation burn, would put the Gemini far ahead of the booster half a rev later and would repeat this relative position every full rev. So a posigrade burn (forward in the direction of orbital travel) would be aimed safely away from the booster and debris, if made at this point in the relative motion profile.

But this didn't happen. When the big posigrade burn was made, the Gemini almost immediately encountered the booster and its debris cloud. Calculating relative motion during the burn based on acceleration and burn time, they would have moved only 600- 800 ft in the +X LVLH frame when they ran into the cloud. They couldn't have been far away from the debris when they started the burn.

A review of all the earlier crew reports on relative position suggests that their VBAR crossing point was migrating down the second stage's -VBAR (behind it on its flight path) with unexpected speed. The football maneuver had been initiated from a leading position (the Gemini was on the booster's +VBAR). But after one rev, the booster was reported to be "ahead" (i.e., the Gemini already was on its -VBAR). After two revs, it was "aways out" ahead (i.e., the Gemini was far down the booster's -VBAR). Nobody at the time noticed the discrepancy.

After two and a half revs, a posigrade burn immediately sent the Gemini through the debris cloud. This suggests that when they had returned to the VBAR on the far end of the football, the entire football had already migrated so far backwards that they were still on the stage's -X VBAR even at this point. Their pre-planned posigrade burn therefore unexpectedly (and perilously) took them not AWAY from the booster/debris as planned, but right TOWARD it, risking recontact.

This shifting of the Gemini football versus the booster/debris would have to occur under the influence of several factors. The translation venting would have been indeterminable (but probably canceled out). However, the small unplanned posigrade sep burn component of 2 ft/sec (due to the Gemini's attitude error at the start of the maneuver) was enough to put them about six miles behind after only two revs, and since the "football" was only five miles long, this alone could account for winding up on the wrong side of the booster. Differential drag would have tended to move the booster and debris into lower, faster orbits, also pulling them ahead of the Gemini, which would have wound up far behind on the VBAR.

The net result of this long-post-flight reanalysis is that the designed placement of the perigee adjust posigrade burn was imprudent and naive, and in hindsight opened the mission to the possibility of spacecraft/booster recontact at rates of 60 to 80 ft/sec This could have resulted in major damage, up to and including vehicle/crew loss. But space is big and tumbling, venting boosters scatter their debris widely, and the odds against recontact were high enough, and the only result was crew surprise, temporary alarm, and subsequent lesson learning.

Following this last burn, the crew saw nothing more of their Titan-2 booster or any associated debris or propellant ice flakes. They were gone forever.


Historical Significance: Eleven days later, the Gemini-6 rendezvous with Gemini-7 made history, and that epochal accomplishment eclipsed this little-known episode. But in terms of historical "firsts", Borman and Lovell had:

* Performed the first stationkeeping with another spacecraft.

* Performed the first controlled separation from another spacecraft.

* Flown the first "football" relative motion trajectory.

* Performed prox ops with a tumbling, venting spacecraft.

These events have now been reconstructed and documented both for purposes of complete history and for purposes of "lessons learned" for future orbital operations, such as using this experience with a venting stage in an STS contingency. By remembering the mistakes of the past, we're supposed to be able to avoid repeating them. By honoring the successes of the past, we are motivated to outdo them. We're better off both ways.

The original trajectory reconstruction memo was sent to both crewmen for their comments in early 1994, and they both responded cordially in writing, agreeing that the study fully and accurately explained their experiences on the Gemini-7 mission.


The "UFO" Version: Meanwhile, curiously, the "bogey" story evolved into an independent legend all its own. This "UFO" case was endorsed by America's leading "ufologist", Northwestern University astronomy professor Dr. J. Allen Hynek, in his book "Edge of Reality" (coauthored with Jacques Vallee, Regnery, 1974), with a new twist. In a chapter ironically titled "Scientists at Work", Hynek includes a list of "astronaut UFO sightings" compiled by amateur investigator George Fawcett. Hynek later insisted he had no need to check the list himself since he just wanted to spark debate, and that readers were wrong to assume that he thought the list was authentic.

This version was repeated by authors such as Donald Keyhoe and Charles Berlitz, and is now widespread in the "UFO literature". For example, in the magazine UFO UNIVERSE (Summer 1994), Brad Steiger (in "Alien Efforts to Undermine Earth's Space Programs") wrote: "When astronauts James Lovell and Frank Bormann (JEO: sic!) were orbiting aboard GT-7 on December 4, 1965, a massive spherical object (JEO: sic!) slowly crossed in front of them. When Bormann radioed ground control that they had a 'bogey' at ten o'clock high, control technicians suggested that the astronauts might be sighting their booster rocket. 'We know where the booster is', Bormann said coolly. 'This is an actual sighting'." The addition of spurious details ("large, spherical object") and elaboration of the astronauts' words is a common feature of such folklorization.


Forgeries: Popular writer Robert Anton Wilson (in "Cosmic Trigger", And/Or Press, 1978) describes the 'Fawcett List' used by Hynek as "NASA cases [which] fall in the category of craft that look and act like spaceships from elsewhere, as Dr. Hynek, who collected them from Air Force files, has indicated." Of course, Hynek hadn't gotten them from such a source, as he himself said, but it made a much better story the way Wilson improved on it. For Wilson, his "Item #10" was as follows: "December 4, 1965 - Gemini 7: Frank Borman and Jim Lovell photographed twin oval-shaped UFOs with glowing undersides."

Now, where did THAT part of the Gemini-7 story come from? I tracked that down some twenty years ago, and published the results, but the story continues to flourish. My main study was in SEARCH magazine, Winter 1976 (issue #129), Palmer Publications, article "Astronauts & UFOs -- The Whole Story", and a shorter version appeared in "Space World" magazine in July 1977.

I wrote: ". . .Only a partisan digging for evidence, and desperate to find such evidence, would make much of this common event. But a sign of desperation is indeed found in connection with the Gemini 7 UFO case. It is not the desperation of government officials trying to cover up the truth about UFOs. Rather, it is the desperation of some outsider trying to manufacture counterfeit 'astronaut UFO' evidence, an activity which should not be necessary if the 'real' UFO evidence were as persuasive as many think."

"It involves a photograph showing two very strange glowing objects. Each is hexagonal in shape, viewed at an angle, and supported by a dazzling 'force field' below it. A cloud covered earth is seen in the background.

"This photograph has appeared in books, magazines, newspapers and pamphlets. It is part of the traveling slide show of UFO lecturers from the Mutual UFO Network (MUFON) and elsewhere. I have heard it described as 'showing a typical UFO force field propulsion system', and 'similar to other UFO photographs taken on Earth the same year.'

"The photograph is a forgery. It is a hoax. What the anonymous counterfeiter did was take an ordinary photograph of Earth made from the Gemini-7 spaceship on December 4, 1965. The nose of the spacecraft fills the lower part of the frame, and on the nose, catching the glare of the sun, is a pair of roll control rocket thrusters used to adjust the attitude and spin rate of the Gemini. The original photo (NASA S65-63722, which I have personally examined) was then retouched by the unscrupulous hoaxter to eliminate the edge of the nose from view, so the dark surface of the spaceship merged into the dark Earth beneath. This left the two now mysterious lights seemingly suspended in space, as it were. A normal space tourist photo was turned into convincing UFO evidence, and thousands of people were fooled."


Conclusion: We are where we are now because of events in the past, and our ideas and impressions of those events often bear only a dim, distant relation to the actual events. The remarkable pioneering space maneuvers of Gemini-7's first few hours in orbit are a striking example of this. The effort to clarify the real past, and to correct our ignorance and misunderstanding of it, pays dividends in a more realistic appraisal of our present state and a better guide for actions in the future. It is also gratifying to assign proper credit for forgotten achievements which helped lay the foundation for historic triumphs such as Apollo. Furthermore and finally, it is immensely satisfying to cast light into dark corners and, as with Borman's now-famous "bogey", to discover and document the reality behind any mystery and myth.



_____________________________________________________________ Documentation:

Gemini VII Technical Debriefing, Dec 23, 1965, originally classified 'Confidential', downgraded to 'unclassified' on Feb 6, 1978.

Gemini Program Mission Report, Gemini VII, January 1966, document MSC-G-R-66-1.

Flight film of the booster is on roll "TBD". As the "first prox ops", it deserves an honorable place in the manned spaceflight history file.

"Shirtsleeve Garb Eases Tasks in Gemini 7", Erwin Bulban, Aviation Week & Space Technology, December 13, 1965, pp. 30-31.

Gemini 8 May Still Go in February", anon., Missiles and Rockets, December 13, 1965, pp. 12-14.

Dr. Edward Condon, project director, "Scientific Study of Unidentified Flying Objects", Bantam, 1969.


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