GRUMMAN PROPOSAL FOR
OPTICAL SURVEILLANCE
Of The
RETROGRADE SATELLITE



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FOREWORD

On 25 August 1960, an unidentified retrograde satellite appeared on photographs taken by the master station of Grumman's Optical Surveillance System.   The photographic plates (shown here) and written reports of several visual sightings of the object were transmitted soon after to SPACE TRACK at L. G. Hanscom Field for official identification.   Analysis of the data there revealed no clue to the satellite's history; its identity remained unknown.

Air Force interest continued, however, and on 19 October 1961, Major Robert Friend of the Foreign Technology Division, Wright-Patterson AFB, and Dr.  J. Allen Hynek, USAF consultant, discussed the problem with us during a visit to our Bethpage engineering offices.    As a result of this meeting, Grumman intensified its efforts to learn more about the satellite's characteristics and to gather data which, hopefully, would lead to positive identification.

This document records the results of initial studies performed since that time and proposes a plan for capturing the satellite.

SECTION   1   SUMMARY

The Grumman Aircraft Engineering Corporation proposes to photograph and identify the unknown retrograde satellite seen repeatedly from June 1960 to June 1961.   We can accomplish this objective in about four-and-one-half months through a three-phase program which we believe will assure a 99-percent probability of success during the search effort.   This program will consist of:

Phase I     Further study of visual and photographic data to establish more accurately
                the orbital parameters of the retrograde object.
Phase II    Optical surveillance at optimum time and period to obtain photographs of the
                object.   (The search program will be defined by a probability analysis of the
                data developed in Phase I.)
Phase III  Study and analysis of all surveillance photographs to identify the retrograde
                satellite and obtain refined orbital parameters.

We intend to carry out our objectives in the following manner:

(1)      Use existing manpower and IBM 7090 facilities combined with inputs from Air
           Force surveillance centers to complete the Phase I orbital calculations.
(2)      Modify existing equipment into a surveillance network.
(3)      Conduct the photographic missions by operating the network.
(4)      Perform both quick-look and detailed analysis of the recorded data.
(5)      Report and document the results.

This plan sets forth what we believe is a realistic, economical means to solve the problem at hand in the immediate future using available equipment and proven techniques.   We recognize that superior electro-optical devices will become available within the next decade, but to await their arrival would be impractical and offer no advantage over the plan proposed for the prime objective.

Then too, with the proposed program, it is possible that the greatest benefits might come from the capture of other objects, such as silent satellites and debris now circling the Earth along uncharted paths.   However, the prime target of the planned search will be the retrograde satellite.

Upon completing the program, Grumman will establish positively, either:   (1)   the orbital parameters of the retrograde satellite and some of its physical characteristics, or (2) the fact that the object has re-entered the Earth's atmosphere and no longer exists.

SECTION 1 IMPLEMENTATION

2.1     Background

Studies to date on the retrograde satellite have accounted for all available visual sightings and three photographic observations.   Because many of these inputs have been found to be in error (including a set of photographs from England), determination of the satellite's orbital elements has depended upon the Grumman photograph (refer to proposal FOREWORD) and what appear to be reliable sightings made by MOONWATCH observers (table 1).

These data reveal a stable orbit, permitting Grumman's optical surveillance system to photograph the object along any segment during acceptable viewing periods.   Assuming no weather interruptions, a probability study (Appendix A) has shown that if the sky is surveyed twice a day for 30-minute periods over 50 days, there is a 99-percent assurance of capturing the satellite.

2. 2     Study Phase

Following confirmation of USAF interest in October 1961, the study effort was devoted to fitting a satisfactory orbit to several selected pairs of observation sites.   To arrive at a first approximation of the satellite's orbital elements, only those observations made during the same time period from widely separated stations were considered necessary. With this method, there is an inherent, though not serious, pitfall; that is, the choice of synodic period is liable to error because it may be, in reality, a fractional multiple of that selected to fit the observations.   In addition, other elements will vary directly with the synodic period, as explained in Appendix B.





The choice of synodic period does not materially affect the probability of capture (Appendix A), but it does affect the accuracy of orbital-element data.   Hence, once the satellite is captured, more exact determination of the synodic period will permit rapid establishment of precise orbital data.

The proposed study program will pursue two immediate objectives:

      1.    To reconcile the computed elements to observations separated by long periods of time.    This can be done by trial-fitting the elements to widely spread observations using an existing IBM 7090 prediction program that accounts for cone of visibility, lighting conditions, and slant-range of the satellite.   Slant range can be adjusted to keep the object's apparent magnitude within the capability of the MOONWATCH observations.

      2.   To incorporate data not previously available.

2.3        Operational Phase

2.3.1    Equipment

Grumman's optical surveillance equipment today comprises a reliable, simple system which has been successfully field-feasted during the past three years in several tracking operations along the Atlantic coast.

Valuable scientific data has been gathered on the following types of space experiments:

*   Sodium vapor clouds, Wallops Island
*   Inflatable satellite ballistic shots (SHOTPUT series), Wallops Island
*   Juno 2 orbital shot, Cape Canaveral
*   AVT-1 (Echo 2 ballistic shot),  Cape Canaveral
*   High-altitude rocket smoke trail dispersion, Wallops Island and Cape Canaveral
*   Majority of the artificial Earth satellites in orbit
FOREWORD
*   Atmospheric re-entry (TRAILBLAZER series), Wallops Island
*   "Lost" satellites, (Discoverer V capsule)

The same components used for these observations would form the major part of the hardware to be incorporated in the proposed satellite surveillance system.

The heart of the system consists of Fairchild K37 aerial cameras with Kodak Aero Ektar (f2.5) 300 mm lenses. (See figure 1.)   These have been modified by the addition of high-speed pulsing shutters into a ballistic-type system which gives excellent performance in space-tracking operations.   Each camera is filled with an ASA magazine with a capacity of 200 feet of film and the ability to be recycled from a remote point.    These units can survey the entire sky above 20 degrees elevation for several hours without interruption, and record passing aircraft and space objects with a timing accuracy approaching ± 2 milliseconds of absolute time.





Using very high-speed film (ASA 1600) this system has easily recorded Explorer IX ("Polkadot") at 2000 miles slant range.   (See figure 2.)   Grumman owns 26 of the modified cameras outright.    The cameras presently respond to a star magnitude of +13.   Although satellite registration is a direct function of angular rate as viewed from the station, the angular rate and apparent magnitude of the retrograde satellite lie well within the limitations of the camera system throughout all portions of the computed orbit.    This does not hold true for visual sightings.




Surveillance at sites chosen for optimum latitude and weather conditions can be accomplished with Grumman1 s mobile tracking van.   (See figure 3.)   Redundancy of certain components in the system (figure 4) guarantees 99-percent operational expectancy during search periods and the design of the system permits equipment to be serviced in the field. This unit successfully operated in the field during the recent BIGSHOT AVT-1 (Echo 2 inflation test) launch from Cape Canaveral.   It is equipped with timing apparatus, independent electrical power supply, vacuum pumps for film magazine operation, antennas, radio receivers, and recording equipment.

The van contains the complete timing and recording gear required to operate the pulsing shutters of two independent banks of surveillance cameras.   The firing pulse is fed to the cameras in a non-repetitious code, making possible positive identification of a satellite photographic image with respect to absolute time and direction.





2.3.2. Timing

A temperature-controlled crystal standard provides the basis for data reference to absolute time.   The standard is periodically synchronized with the time signal of the Naval Observatory.   A one-pps signal generated by the standard triggers the camera shutters.  Instead of being fed directly to the cameras, this pulse passes through an encoder which gates only selected pulses.   In this manner, a photographic trace on the film will carry its own coded series of time breaks to facilitate rapid identification in absolute time when compared to oscillograph tapes which monitor the entire pulsing system.

It is through this positive identification method which employs a non-repetitive code that the operator can rapidly identify photographed objects.in both time and direction.

2.3.3.  Location

The area considered best for carrying out the surveillance program is Edwards Air Force Base, California.   This installation not only lies within the optimum latitude range for tracking satellites, (except those in low equatorial orbits) but offers excellent year-round weather and atmospheric clarity—distinct advantages to a surveillance operation of this type.   In addition, Grumman personnel who will be running the program are thoroughly familiar with the transportation, supply and housing facilities at the base, having conducted several demonstrations for the military there in the past.

Were it not for the unreliable weather conditions on Long Island, the photographic surveillance could also be accomplished at Grumman using the same equipment intended for the field operation.   Working from a home base has decided advantages, but weather delays would stretch the surveillance period considerably.   (Refer to Appendix A.)

2.3.4 Period

Figures A-7 and A-8 of Appendix A define two optimum operational periods for capture of the retrograde satellite: 30 minutes and 120 minutes.    We have chosen a 30-minute period based on our present knowledge, past experience in satellite tracking, and intuitive reasoning.    Not only is it more economical in manpower required for data inspection but it minimizes interference of the shadow cone corridor which is expected to sharply limit the period of visibility when the satellite is near perigee.

2.3.5    Operating Sequence

A typical operating sequence would begin with two independently powered banks of nine cameras each oriented to cover the entire sky above 20 degrees elevation.   (See figure 5.) Bank "A" is energized at the start of the prescribed search period with the encoded pulse operating all nine shutters simultaneously.   With each camera covering a 45-degree cone of view, little or no chance exists for even the lower, high-angular-rate space objects to escape detection.






When effective exposure of the film approaches the upper safe limit of the emulsion, the film magazines are remotely recharged.   Because average film transport time in only three seconds, no appreciable gap is left in sky coverage.

During the rest period required to change film magazines or otherwise service the cameras, Bank "B" is put into operation.   This bank is situated remotely from Bank "A" and is also controlled from within the van.

Exposed film, estimated at 200 to 400 feet per day of operation, will be processed and studied prior to beginning the next day's operation.   In this way, information revealed by the film can be transmitted without delay to alert other tracking complexes through NORAD.

The data obtained by the cameras will be given quick-look inspection by experienced Grumman observers.





Any object in a retrograde orbit will show up immediately during this inspection as a result of the rapid identification process made possible by the simple pulsed-code shutter system.   An example of this feature is shown in figure 6.

Although the retrograde satellite will be the primary target during the search, all objects exhibiting satellite-like characteristics will be catalogued.    To avoid duplication of the NORAD effort, only such data as right ascension, declination and absolute time will be dispatched.   It is expected that NORAD will match these inputs with known satellite orbits and immediately advise the surveillance station if an unidentified object is detected.   In such cases, the objects's trajectory will be scrutinized more carefully by the surveillance station through photogrammetric reduction of the negative.

Following detection of the unidentified satellite, the last phase of the program will be brought into play with a study and analysis of all preceding data leading to identification of the object and definition of its orbital parameters.

SECTION  3  SCHEDULE

The proposed surveillance program, from go-ahead to satellite capture and identification, would take about four-and-one-half months.    Figure 7 shows the milestones of the program and dates of accomplishment based on an assumed starting date of mid-March, 1962.





Appendix A and B