oversight

Theater Missile Defense: Significant Technical Challenges Face the Airborne Laser Program

Published by the Government Accountability Office on 1997-10-23.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

                  United States General Accounting Office

GAO               Report to the Ranking Minority Member,
                  Committee on National Security, House
                  of Representatives


October 1997
                  THEATER MISSILE
                  DEFENSE
                  Significant Technical
                  Challenges Face the
                  Airborne Laser
                  Program




GAO/NSIAD-98-37
             United States
GAO          General Accounting Office
             Washington, D.C. 20548

             National Security and
             International Affairs Division

             B-275849

             October 23, 1997

             The Honorable Ronald V. Dellums
             Ranking Minority Member
             Committee on National Security
             House of Representatives

             Dear Mr. Dellums:

             As you requested, this report discusses our review of the status of the
             Airborne Laser (ABL) program. The Department of Defense (DOD) plans to
             develop the ABL as its primary program for intercepting theater ballistic
             missiles shortly after they have been launched—also known as the boost
             phase. The Air Force estimates the life-cycle cost of the ABL program to be
             about $11 billion. That estimate includes $1.3 billion for the program
             definition and risk reduction phase, $1.2 billion for the engineering and
             manufacturing development phase, $3.8 billion for the production phase,
             and $4.9 billion for 20 years of operations and support.

             This report discusses (1) the way in which the ABL is expected to change
             theater missile defense, (2) assurances that the ABL will be able to operate
             effectively in the levels of optical turbulence that may be encountered in
             the geographical areas in which the system might be used, and (3) the
             technical challenges in developing an ABL system that will be compatible
             with the unique environment of an aircraft.


             Operation Desert Storm demonstrated that the U.S. military and other
Background   allied forces have limited capability against theater ballistic missiles. In
             fact, U.S. defensive capability is limited to weapons that defend against
             missiles nearing the end of their flight, such as the Patriot. No capability
             currently exists to destroy missiles in the boost phase. Consequently, DOD
             is expending considerable resources to develop the ABL’s capability to
             intercept missiles in their boost phase. In simple terms, the ABL program
             will involve placing various components, including a powerful
             multimegawatt laser, a beam control system, and related equipment, in a
             Boeing 747-400 aircraft and ensuring that all the components work
             together to detect and destroy enemy missiles in their boost phase.

             In November 1996, the Air Force awarded a 77-month program definition
             and risk reduction contract to the team of Boeing, TRW, and Lockheed
             Martin. Under the contract, Boeing is to produce and modify the 747-400




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                   aircraft and integrate the laser and the beam control system with the
                   aircraft, TRW will develop the multimegawatt Chemical Oxygen Iodine
                   Laser (COIL) and ground support systems, and Lockheed Martin will
                   develop the beam control system.

                   The various program components are in the early phases of design and
                   testing. One prototype ABL will be produced and used in 2002 to shoot
                   down a missile in its boost phase. If this demonstration is successful, the
                   program will move into the engineering and manufacturing development
                   phase in 2003. Production is scheduled to begin about 2005. Initial
                   operational capability of three ABLs is scheduled for 2006; full operational
                   capability of seven ABLs is scheduled for 2008.


                   Although DOD has a long history with laser technologies, the ABL program is
Results in Brief   its first attempt to design, develop, and install a multimegawatt laser on an
                   aircraft. The ABL is also expected to be DOD’s first system to intercept
                   missiles during the boost phase. To successfully destroy a missile in its
                   boost phase, the ABL system would have to, within about 30 to 140
                   seconds, detect a missile shortly after it has been launched several
                   hundred kilometers away, track the rising missile’s path, and hold a
                   concentrated laser beam on the missile until the beam’s heat causes the
                   missile’s pressurized casing to fracture and then explode. This explosion
                   would then cause a missile’s warhead, along with any nuclear, chemical,
                   or biological agents it may contain, to fall short of the intended target and
                   possibly back on the aggressor’s territory.

                   A key factor in determining whether the ABL will be able to successfully
                   destroy a missile in its boost phase is the Air Force’s ability to predict the
                   levels of turbulence that the ABL is expected to encounter. An accurate
                   prediction of those turbulence levels is needed to define the ABL’s
                   technical requirements for turbulence. To date, the Air Force has not
                   shown that it can accurately predict the levels of turbulence the ABL is
                   expected to encounter or that its technical requirements regarding
                   turbulence are appropriate.

                   The turbulence that the ABL will encounter is referred to as optical
                   turbulence. This type of turbulence can be measured either optically or
                   non-optically. Optical measurements are taken by transmitting laser beams
                   from one aircraft to instruments on board another aircraft at various
                   altitudes and distances. Non-optical measurements of turbulence are taken
                   by radar or by temperature probes mounted on balloons or on an aircraft’s



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exterior. The Air Force has taken both optical and non-optical
measurements for the ABL program. However, because the ABL is an optical
weapon system, only optical measurements of turbulence can measure the
turbulence that will actually be encountered by the ABL laser beam along
its path. The Air Force has no plans to take additional optical
measurements. Instead, it plans to take additional non-optical
measurements to predict the severity of optical turbulence the ABL will
encounter. Therefore, to ensure that the non-optical measurements can be
validly applied to the ABL program, the Air Force must determine whether
the non-optical measurements can be correlated to optical measurements.
A senior-level ABL oversight team has expressed concern about the
absence of such a correlation. In response, the Air Force has indicated
that it plans to determine, in late 1997, whether a correlation exists
between optical and non-optical measurements.

Until the Air Force can verify that its predicted levels of optical turbulence
are valid, it will not be able to validate the ABL’s design specification for
overcoming turbulence. The Air Force has established a design
specification for the ABL that is based on Air Force modeling techniques.
However, data collected by the program office indicate that the levels of
turbulence the ABL may encounter could be four times greater than the
levels in which the system is being designed to operate. According to DOD
officials, if the higher levels of optical turbulence are encountered, the
effective range of the ABL system would decrease, and the risk that the ABL
system would be underdesigned for its intended mission would increase.
DOD officials also indicated that a more realistic design may not be
achievable using current state-of-the-art technology.

In addition to the challenges posed by turbulence, developing and
integrating a laser weapon system into an aircraft pose many technical
challenges for the Air Force. The Air Force must build a new laser that is
able to contend with size and weight restrictions, motion and vibrations,
and other factors unique to an aircraft environment and yet be powerful
enough to sustain a killing force over a range of at least 500 kilometers.
Also, the Air Force must create a beam control system that must
compensate for the optical turbulence in which the system is operating
and control the direction and size of the laser beam. The beam control
system will consist of complex software programs, moving telescopes, and
sophisticated mirrors. To date, the Air Force has not demonstrated how
well a beam control system of such complexity can operate on an aircraft.
Because these challenges will not be resolved for several years, it is too




Page 3                                    GAO/NSIAD-98-37 Theater Missile Defense
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                   early to accurately predict whether the ABL program will evolve into a
                   viable missile defense system.


                   The ABL is a complex laser weapon system that is expected to detect an
The ABL Is a New   enemy missile shortly after its launch, track the missile’s path, and destroy
Weapon Concept     the missile by holding a concentrated laser beam on it until the beam’s
                   heat causes the pressurized missile casing to crack, in turn causing the
                   missile to explode and the warhead to fall to earth well short of its
                   intended target.

                   The ABL’s opportunity to shoot down a missile lasts only from the time the
                   missile has cleared the cloud tops until its booster burns out.1 That
                   interval can range from 30 to 140 seconds, depending on missile type.
                   During that interval, the ABL is expected to detect, track, and destroy the
                   missile, as shown in figure 1.




                   1
                    The missile’s booster is under pressure only while it is burning. This pressure causes the missile to
                   explode after heat from the laser fractures the casing.



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                                   B-275849




Figure 1: ABL Missile Engagement

  Altiude (feet)
                                                           Window of opportunity
                                                             30 to 140 seconds
      120,000




                                                             Booster burnout

      100,000




       80,000
                                                                 Missile
                                                                destroyed
                                                                                          Destruction

       60,000                                                  Laser Dwell


                                                                                          Tracking
                    747


       40,000


                                                                                          Detection
                                              Cloud Tops

       20,000




                                   Page 5                        GAO/NSIAD-98-37 Theater Missile Defense
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The first step—detection—is to begin when the ABL’s infrared search
sensor detects a burst of heat that could be fire from a missile’s booster.2
Because clouds block the view of the infrared search sensor, the sensor
cannot detect this burst of heat until the missile has broken through the
cloud tops—assumed to be at about 38,500 feet. The sensor detects the
heat burst about 2 seconds after the missile has cleared the cloud tops. (In
the absence of clouds, detection can occur earlier.) The ABL would then
use information from the sensor to verify that the heat burst is the plume
of a missile in its boost phase and would then move the telescope located
in the nose of the aircraft toward the coordinates identified by the infrared
sensor.

The second step—tracking—is to be performed sequentially and with
increasing precision by several ABL devices. The first of these tracking
devices, the acquisition sensor, is to take control of the telescope, center
the plume in the telescope’s field of view, and hand off that information to
the next device, the plume tracker.

The plume tracker, having taken control of the telescope, is to track and
determine the shape of the missile plume and use this information to
estimate the location of the missile’s body and project a beam from the
track illuminator laser to light up the nose cone of the missile. The plume
tracker is then to hand its information, and control of the telescope, to the
final tracking device, the fine tracker.

The fine tracker is to measure the effects of turbulence and determine the
aimpoint for the beacon laser and, ultimately, for the COIL laser. The
reflected light from the illuminator laser provides information that is to be
used to operate a sophisticated mirror system (known as a fast-steering
mirror) that helps to compensate for optical turbulence by stabilizing the
COIL beam on the target. The reflected light from the beacon laser provides
information that is to be used to operate deformable mirrors that will
further compensate for turbulence by shaping the COIL beam.3 With the
illuminator and beacon lasers still operating, the fine tracker is to
determine the aimpoint for the COIL laser. The COIL laser is to be brought to
full power and focused on the aimpoint.


2
Even though the ABL’s surveillance system will be the primary means for detecting missiles, the ABL
will also have the capability to accept missile detection information from other DOD sensor systems.
3
 A deformable mirror is a flexible reflective surface mounted to an array of actuators, or pistons, that
can rapidly (up to 1,000 times per second) alter the shape of the mirror. In effect, the mirror’s shape is
altered to predistort an outgoing laser beam, which is then refocused by the turbulence through which
the beam travels on its way to the target.



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                          At this point, the final step in the sequence—missile destruction—is to
                          begin. During this final step, a lethal laser beam is held on the missile. The
                          length of time that the beam must dwell on the missile will depend on
                          turbulence levels and the missile type, hardness, range, and altitude.
                          Throughout the lethal dwell, the illuminator and beacon lasers are to
                          continue to operate, providing the information to operate the fast-steering
                          and deformable mirrors. Under the intense heat of the laser beam, which is
                          focused on an area about the size of a basketball, the missile’s pressurized
                          casing fractures, and then explodes, destroying the missile.

                          The ABL is expected to operate from a central base in the United States and
                          be available to be deployed worldwide. The program calls for a
                          seven-aircraft fleet, with five aircraft to be available for operational duty at
                          any given time. The other two aircraft are to be undergoing modifications
                          or down for maintenance or repair. When the ABLs are deployed, two
                          aircraft are to fly, in figure-eight patterns, above the clouds at about
                          40,000 feet. Through in-flight refueling, which is to occur between 25,000
                          and 35,000 feet, and rotation of aircraft, two ABLs will always be on patrol,
                          thus ensuring 24-hour coverage of potential missile launch sites within the
                          theater of operations. The ABLs are intended to operate about
                          90 kilometers behind the front line of friendly troops but could move
                          forward once air superiority has been established in the theater of
                          operations. When on patrol, the ABLs are to be provided the same sort of
                          fighter and/or surface-to-air missile protection provided to other
                          high-value air assets, such as the Airborne Warning and Control System
                          and the Joint Surveillance Target Attack Radar System.


                          A key factor in determining whether the ABL will be able to successfully
ABL’s Operational         destroy a missile in its boost phase is the Air Force’s ability to predict the
Effectiveness Is          levels of turbulence that the ABL is expected to encounter. Those levels are
Currently Unknown         needed to define the ABL’s technical requirements for turbulence. To date,
                          the Air Force has not shown that it can accurately predict the levels of
                          turbulence the ABL is expected to encounter or that its technical
                          requirements regarding turbulence is appropriate.


Correlation Between       The type of turbulence that the ABL will encounter is referred to as optical
Non-Optical and Optical   turbulence. It is caused by temperature variations in the atmosphere.
Turbulence Measurements   These variations distort and reduce the intensity of the laser beam. Optical
                          turbulence can be measured either optically on non-optically. Optical
Is Needed                 measurements are taken by transmitting laser beams from one aircraft to



                          Page 7                                     GAO/NSIAD-98-37 Theater Missile Defense
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instruments on board another aircraft at various altitudes and distances.
Non-optical measurements of turbulence are taken by radar or by
temperature probes mounted on balloons or on an aircraft’s exterior.

The Air Force’s ABL program office has not determined whether
non-optical measurements of turbulence can be mathematically correlated
with optical measurements. Without demonstrating that such a correlation
exists, the program office cannot ensure that the non-optical
measurements of turbulence that it is collecting are useful in predicting
the turbulence likely to be encountered by the ABL’s laser beam.

Concern about turbulence measurements was expressed by a DOD
oversight office nearly 1 year ago. In November 1996, during its
milestone 1 review of the ABL program,4 the Defense Acquisition Board
directed the program office to develop a plan for gathering additional data
on optical turbulence and present that plan to a senior-level ABL oversight
team for approval. The Board also asked the program office to
“demonstrate a quantifiable understanding of the range and range
variability due to optical turbulence and assess operational implications.”
This requirement was one of several that the Air Force has been asked to
meet before being granted the authority to proceed with development of
the ABL. That authority-to-proceed decision is scheduled for June 1998.

In February 1997, the program office presented to the oversight team a
plan for gathering only non-optical data. The oversight team accepted the
plan but noted concern that the plan was based on a “fundamental
assumption” of a correlation between non-optical and optical
measurements. If that assumption does not prove to be accurate,
according to the oversight team, the program office will have to develop a
new plan to gather more relevant (i.e., optical rather than non-optical)
measurements. Accordingly, the oversight team required that the program
office include in its data-gathering plan a statement agreeing to
demonstrate the correlation between the non-optical and optical
measurements. Program officials said they plan to demonstrate that
correlation in the summer of 1997.

To establish that a correlation exists, the program office plans to use
optical and non-optical turbulence measurements taken during a 1995 Air
Force project known as Airborne Laser Extended Atmospheric
Characterization Experiment (ABLE ACE). Optical measurements were made
by transmitting two laser beams from one aircraft to instruments aboard

4
 This review is the point in time at which a new acquisition program is approved.



Page 8                                                 GAO/NSIAD-98-37 Theater Missile Defense
                         B-275849




                         another aircraft at distances from 13 to 198 kilometers and at altitudes
                         from 39,000 to 46,000 feet. These measurements provided the data used to
                         calculate the average turbulence strengths encountered by the beams over
                         these distances.

                         The ABLE ACE project also took non-optical measurements of turbulence
                         using temperature probes mounted on the exterior of one of the aircraft.
                         Rather than taking measurements over the path of a laser beam between
                         two aircraft, as with the optical measurements, the probes measured
                         temperature variations of the air as the aircraft flew its route.

                         Opinions vary within DOD about whether a correlation between optical and
                         non-optical turbulence measurements can be established. Some
                         atmospheric experts, who are members of the program office’s Working
                         Group on Atmospheric Characterization, criticized the program office’s
                         plan for collecting additional atmospheric data because it did not include
                         additional optical measurements. Minutes from a Working Group meeting
                         indicated that some of these experts believed that “current scientific
                         understanding is far too immature” to predict optical effects from
                         non-optical point measurements. In contrast, the chief scientist for the ABL
                         program said it would be surprising if the two measurements were not
                         directly related; he added that evaluations at specific points in the ABLE ACE
                         tests have already indicated a relationship. According to the chief scientist,
                         it would be prudent for the program office to continue to collect
                         non-optical data while it completes its in-depth analysis of the ABLE ACE
                         data.

                         According to a DOD headquarters official, because the ABL is an optical
                         weapon, gathering non-optical data without first establishing their
                         correlation to optical data is risky. The official concluded that, if the
                         program office cannot establish this correlation, turbulence data will have
                         to be gathered through optical means.


Technical Requirements   The ABL program office also has not shown that the turbulence levels in
for Overcoming           which the ABL is being designed to operate are realistic. Available optical
Turbulence May Be        data on optical turbulence indicate that the turbulence the ABL may
                         encounter could be four times greater than the design specifications.
Understated              These higher levels of optical turbulence would decrease the effective
                         range of the ABL system.




                         Page 9                                    GAO/NSIAD-98-37 Theater Missile Defense
B-275849




The ABL program office set the ABL’s design specifications for optical
turbulence at a level twice that, according to a model, the ABL would likely
encounter at its operational altitude. This model was based on research
carried out in 1984 for the ground based laser/free electron laser program,
in which non-optical measurements were taken by 12 balloon flights at the
White Sands Missile Range in New Mexico. Each of the 12 flights took
temperature measurements at various altitudes. These measurements
were then used to develop a turbulence model that the program office
refers to as “clear 1 night.”

The clear 1 night model shows the average turbulence levels found at
various altitudes. The ABL is being designed to operate at about
40,000 feet, so the turbulence expected at that level became the starting
point for setting the design specifications. To ensure that the ABL would
operate effectively at the intended ranges, for design purposes, the
program office doubled the turbulence levels indicated by its clear 1 night
model. The program office estimated that the ABL could be expected to
encounter turbulence at or below that level 85 percent of the time. This
estimate was based on the turbulence measured by 63 balloon flights made
at various locations in the United States during the 1980s.

When the ABL design specifications were established, the program office
had very little data on turbulence. However, more recent data,
accumulated during the ABLE ACE program, indicated that turbulence levels
in many areas were much greater than those the ABL is being designed to
handle. According to DOD officials, if such higher levels of turbulence are
encountered, the effective range of the ABL system would decrease, and the
risk that the ABL system would be underdesigned for its intended mission
would increase. DOD officials also indicated that a more realistic design
may not be achievable using current state-of-the-art technology.

ABLE ACE  took optical measurements in various parts of the world,
including airspace over the United States, Japan, and Korea. According to
the program office and Office of the Secretary of Defense (OSD) analyses of
optical measurements taken during seven ABLE ACE missions, overall
turbulence levels exceeded the design specifications 50 percent of the
time. For the two ABLE ACE missions flown over Korea, the measurements
indicated turbulence of up to four times the design specifications.
Additionally, according to officials in OSD, ABLE ACE data were biased
toward benign, low-turbulent, nighttime conditions. According to these
officials, turbulence levels may be greater in the daytime.




Page 10                                  GAO/NSIAD-98-37 Theater Missile Defense
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                  Developing and integrating a weapon-level laser, a beam control system,
Developing and    and the many associated components and software systems into an
Integrating ABL   aircraft are unprecedented challenges for DOD. Although DOD has
Components Pose   integrated a weapon-level laser and beam control system on the ground at
                  White Sands Missile Range, it has not done so in an aircraft environment.
Many Technical    Therefore, it has not had to contend with size and weight restrictions,
Challenges        motion and vibrations, and other factors unique to an aircraft
                  environment.

                  The COIL is in the early development stage. The Air Force must build the
                  laser to be able to contend with size and weight restrictions, motion and
                  vibrations, and other factors unique to an aircraft environment, yet be
                  powerful enough to sustain a killing force over a range of at least
                  500 kilometers. It is to be constructed in a configuration that links
                  modules together to produce a single high-energy beam. The laser being
                  developed for the program definition and risk reduction phase will have
                  six modules. The laser to be developed for the engineering and
                  manufacturing development phase of the program will have 14 modules.
                  To date, one developmental module has been constructed and tested.
                  Although this developmental module exceeded its energy output
                  requirements, it is too heavy and too large to meet integration
                  requirements. The module currently weighs about 5,535 pounds and must
                  be reduced to about 2,777 pounds. The module’s width must also be
                  reduced by about one-third. To accomplish these reductions, many
                  components of the module may have to be built of advanced materials,
                  such as composites.

                  The ABL aircraft, a Boeing 747-400 Freighter, will require many
                  modifications to allow integration of the laser, beam control system, and
                  other components. A significant modification is the installation of the
                  beam control turret in the nose of the aircraft. The beam control turret is
                  to be used for acquisition, tracking, and pointing actions used in
                  destroying a missile. Consequently, the location of the turret is critical to
                  the success of the ABL. Issues associated with the turret include the
                  decreased aircraft performance resulting from the additional drag on the
                  aircraft; the interaction of the laser beam with the atmosphere next to the
                  turret, which can cause the laser beam to lose intensity; and vibrations
                  from the operation of the aircraft that affect the accuracy of pointing the




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                  beam control turret. The contractor has conducted wind tunnel tests of
                  these expected effects for three different turret locations and found that
                  installing the turret in the nose of the aircraft would cause the fewest
                  negative effects. However, the operational effectiveness of the beam
                  control turret will not be known until it undergoes additional testing in
                  2002 in an operationally realistic environment.

                  The laser exhaust system is another critical modification. The system must
                  prevent the hot corrosive laser exhaust from damaging the bottom of the
                  aircraft and other structural components made of conventional aluminum.
                  The exhaust created by the laser will reach about 500 degrees Fahrenheit
                  when it is ejected through the laser exhaust system on the bottom of the
                  aircraft. This exhaust system must also undergo additional testing on the
                  aircraft in 2002 to determine its operational effectiveness.

                  Integrating the beam control system with the aircraft also poses a
                  challenge for the Air Force. The Air Force must create a beam control
                  system, consisting of complex software programs, moving telescopes, and
                  sophisticated mirrors, that will compensate for the optical turbulence in
                  which the system is operating and control the direction and size of the
                  laser beam. In addition, the beam control system must be able to tolerate
                  the various kinds of motions and vibrations that will be encountered in an
                  aircraft environment. In deciding the on-board location of the beam
                  control system’s components, the Air Force used data gathered by an
                  extensive study of aircraft vibrations on the 747-400 Freighter. The beam
                  control components are expected to be located in those areas of the
                  aircraft that experience less intense vibrations and, to the extent possible,
                  be shielded from vibrations and other aircraft motion. To date, the
                  Air Force has not demonstrated how well a beam control system of such
                  complexity can operate on an aircraft. The contractor has modeled the
                  ABL’s beam control system on a brassboard but has not tested it on board
                  an aircraft.5

                  The ABL program is a revolutionary weapon system concept. Although DOD
Conclusions and   has a long history with laser technologies, the ABL is its first attempt to
Recommendations   design, develop, and install a multimegawatt laser on an aircraft. As such,
                  the concept faces a number of technological challenges. A fundamental
                  challenge is for the Air Force to accurately and reliably predict the level of
                  optical turbulence that the ABL will encounter and then design the system
                  to operate effectively in that turbulence. The Air Force will not have

                  5
                   A brassboard is an experimental device (or group of devices) used to determine feasibility and
                  develop technical and operational data. It may resemble the end item but is not intended for use as the
                  end item.



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                      resolved that challenge until it has demonstrated whether there is a
                      reliable correlation between its non-optical and optical turbulence
                      measurements, or, should such a correlation not exist, gather additional
                      optical data, which may delay the ABL program. Whether relevant and
                      reliable data are confirmed through correlation or by additional optical
                      measurements, the data are critical in assessing the appropriateness of the
                      design specifications for turbulence. If the specifications need to be set
                      higher, that should be done as soon as possible.

                      Therefore, we recommend that the Secretary of Defense direct the
                      Secretary of the Air Force to take the following actions:

                  •   Demonstrate as quickly as possible, but no later than the time when DOD
                      decides whether to grant the ABL program the authority to proceed
                      (currently scheduled for June 1998), the existence of a correlation
                      between the optical and non-optical turbulence data. If a correlation
                      between optical and non-optical data cannot be established, the Air Force
                      should be required to gather additional optical data to accurately predict
                      the turbulence levels the ABL may encounter, before being given the
                      authority to proceed with the program as planned.
                  •   Validate the appropriateness of the design specification for turbulence
                      based on reliable data that are either derived from a correlation between
                      optical and non-optical data or obtained through the collection of
                      additional optical data.


                      DOD concurred with both of our recommendations. DOD’s comments are
Agency Comments       reprinted in appendix I. DOD also provided technical comments that we
                      incorporated in this report where appropriate.


                      We reviewed and analyzed DOD, Air Force, ABL program office, and
Scope and             contractor documents and studies regarding various aspects of the ABL
Methodology           program. We discussed the ABL program with officials of the Office of the
                      Under Secretary of Defense (Comptroller); the Office of the Under
                      Secretary of Defense (Acquisition and Technology); the Air Combat
                      Command; the ABL program office; the Air Force’s Phillips Laboratory; and
                      the ABL Contractor team of Boeing, TRW, and Lockheed Martin. We also
                      discussed selected aspects of the ABL program with a consultant to the ABL
                      program office.




                      Page 13                                 GAO/NSIAD-98-37 Theater Missile Defense
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We conducted our review from September 1996 to August 1997 in
accordance with generally accepted government auditing standards.

We are sending copies of this report to the congressional committees that
have jurisdiction over the matters discussed and to the Secretary of
Defense; the Secretary of the Air Force; and the Director, Office of
Management and Budget. We will make copies available to others on
request.

Please contact me at (202) 512-4841 if you or your staff have questions
concerning this report. Major contributors to this report were
Steven Kuhta, Ted Baird, Suzanne MacFarlane, and Rich Horiuchi.

Sincerely yours,




Louis J. Rodrigues
Director, Defense Acquisitions Issues




Page 14                                 GAO/NSIAD-98-37 Theater Missile Defense
Page 15   GAO/NSIAD-98-37 Theater Missile Defense
Appendix I

Comments From the Department of Defense




             Page 16        GAO/NSIAD-98-37 Theater Missile Defense
                Appendix I
                Comments From the Department of Defense




Now on p. 13.




                Page 17                                   GAO/NSIAD-98-37 Theater Missile Defense
                Appendix I
                Comments From the Department of Defense




Now on p. 13.




(707210)        Page 18                                   GAO/NSIAD-98-37 Theater Missile Defense
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