Demonstration of Submarine Control of an Unmanned Aerial Vehicle

SUBMARINE CONTROL OF AN UNMANNED AERIAL VEHICLE

H

Demonstration of Submarine Control of an UnmannedAerial Vehicle

Vincent Vigliotti

ow often does a person onboard a submarine get to fly an airplane? In a uniquedemonstration in June 1996 off the California coast, pilots and payload operators inthe torpedo room of a fast-attack submarine, the USS Chicago (SSN 721), flew aPredator Unmanned Aerial Vehicle (UAV) in support of a Special Operations Forceswarfare exercise. The Applied Physics Laboratory was responsible for the initialconcept of the UAV control system located on a submarine and then led theextremely successful 10-month effort to develop and install this system and conduct anat-sea demonstration.(Keywords: At-sea demonstration, Predator, SSN-UAV, Submarine, UAV.)

INTRODUCTIONImagine the benefit of giving a forward-deployed

fast-attack submarine operating in the shallow littoralzone a 25,000-ft-high, movable periscope (say, out to100 nmi from the submarine). The stealthy submarinewould now be able to extend its “eyes” far out to seaand inland to support a variety of missions, such astactical and intelligence reconnaissance and surveil-lance, Special Operations Forces (SOF) support, strikesupport, and battle damage assessment. This capabilitywas demonstrated in June 1996 in an exercise near SanClemente Island, California, involving a fast-attack(SSN 688 class) submarine, the USS Chicago (SSN721), and the Predator Unmanned Aerial Vehicle(UAV). During this exercise, operators onboard thesubmarine took control of the UAV and demonstratedreal-time piloting, payload control, and viewing ofreal-time imagery. The submarine then used the UAVto support an SOF warfare exercise (SOF laser

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (

designation of target for destruction by aircraft withlaser-guided munitions) against a land-based movablemissile site. The SOF team commander, who was lo-cated on the submarine, used the Predator’s imagery inreal time for mission planning; target location, iden-tification, and tracking; monitoring of SOF team in-gress and egress; and viewing of target destruction andbattle damage assessment. Selected imagery was re-layed in near real time to the Joint Task Force Com-mander (JTFC), who was 3000 miles away.

DEMONSTRATION BACKGROUNDIn August 1994, the Office of Naval Intelligence

(ONI) requested that the Laboratory’s Ocean DataAcquisition Program assess feasibility and developa conceptual design for a demonstration of inter-operability between a fast-attack submarine and the

1998) 501

V. VIGLIOTTI

Predator UAV. The objectives and constraints of thisdemonstration were to

• Establish a submarine-UAV data link, demonstratesubmarine control of a UAV vehicle and its payload,and demonstrate submarine receipt of UAV andpayload status and real-time imagery.

• Pilot the UAV by using existing UAV mission plan-ning software to modify navigation way points. Al-though real-time piloting was not a requirement, thiscapability was, in fact, demonstrated.

• Provide submarine operators with the ability to se-lect and process UAV imagery and to fuse UAVimagery with other submarine data (such as peri-scope imagery or electronic surveillance data fromexisting submarine antennas). The Submarine JointDeployable Intelligence Support System (SUBJDISS) was to be used for onboard data fusion and forinterfacing to the submarine’s satellite commun-ications equipment for subsequent off-board datatransmission.

• Demonstrate the submarine-UAV data link to amaximum of 85 nmi.

• Demonstrate operational and tactical benefitsachieved in SSN missions with UAV support (sup-port an operational exercise).

• Ensure the compatibility of the SSN-UAV demon-stration system with all SSN 688 class submarines.

• Complete the entire demonstration in less than1 year, including design, development, land testing,submarine installation, and at-sea technical and op-erational exercises.

• Achieve these goals without changes to air vehiclehardware or software.

The feasibility assessment, concept design, costestimate, and 10-month development plan were pre-sented in November 1994 to ONI and are documentedby Rau et al.1

In a January 1995 letter to the Joint Program Office(JPO) for Cruise Missiles and UAVs, Admiral Borda,the Chief of Naval Operations (CNO), stated theNavy’s need for a marine variant of the Predator UAV(called UAV “marinization”), and directed the JPO toconduct a detailed study for three levels of operationaldemonstrations:

• Level I: connectivity with land-based UAV assets tocommanders at sea

• Level II: shipboard control of land-based UAV assets(vehicle and payload)

• Level III: shipboard employment (launch and recov-ery) of UAVs

Three options were initially considered for the LevelII demonstration: (1) positioning a ground station ona surface ship (approximate 6-month schedule); (2)going forward with the 10-month APL concept for the

502 JOH

SSN-UAV interaction demonstration; or (3) integrat-ing with the Hunter UAV’s prototype data link/work-station (approximate 24-month schedule). Rear Admi-ral Jones, Director of the Submarine Warfare Division(N87), strongly endorsed the APL proposal in an April1995 letter to the Deputy CNO (N8):

I feel strongly that the integration of an SSN and UAVwould be a tremendous tactical asset . . . . The UAV marin-ization option which utilizes an SSN has the followingadvantages over the other candidates: enables covert line-of-sight control of the UAV from waters which may bedenied to surface units; and provides real time intelligenceonboard the SSN which could greatly enhance war fightingcapability in a variety of missions such as SOF, strikewarfare BDA, and targeting of mobile targets . . . . A suc-cessful near term demonstration could become an impor-tant battle group capability.

The JPO also recommended funding of the Laborato-ry’s near-term demonstration as part of the Predatormarinization.

The general opinion of APL and sponsors was thatdemonstrating Level II marinization from a submarinewas the hardest problem. If shipboard control of land-based UAV assets could be demonstrated from a sub-marine, with its lack of internal and external space andits operational constraints, then such control should bepossible for any tactical platform at sea. In April 1995,APL’s concept for SSN control of the Predator UAVwas selected as the Phase II demonstration in theCNO’s UAV Marinization Plan. In August 1995, ONIand N87 jointly funded APL to lead the team effortfor the submarine-based technical demonstration. Theorganizations involved in this team effort and theirresponsibilities are shown in Table 1.

DESCRIPTION OF THEPREDATOR UAV

The Predator was developed by General Atomics asa 30-month Advanced Concept Technology Demon-stration of a medium-altitude endurance UAV. Thisdemonstration was ongoing during the SSN-UAVdemonstration. The Predator’s primary purpose is toprovide near–real-time imagery intelligence to satisfyreconnaissance, surveillance, and target acquisitionmission requirements.2 The Predator is designed tooperate at long ranges (500-nmi radius of action) andfor extended on-station times (24 h of continuouscoverage at 500 nmi). The UAV system consists of thePredator aircraft and a trailer-housed ground controlstation (GCS). The baseline sensor payload for thePredator includes infrared and color cameras and syn-thetic aperture radar (SAR). The SAR was still underdevelopment during the SSN-UAV demonstration,and was not offered as a possible payload sensor for thisdemonstration. Important characteristics of the Pred-ator are presented in Table 2.

NS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1998)

503

N UNMANNED AERIAL VEHICLE

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1998)

SUBMARINE CONTROL OF A

The Predator supports three types of communica-tions links: C-band line-of-sight (LOS), ultra-highfrequency (UHF) satellite communications (SAT-COM), and Ku-band SATCOM. The 20-MHz band-width of the analog C-band link contains two chan-nels of real-time color video and one audio channelfor control and status data, and it supports real-timepiloting and payload control. The UHF SATCOMlink is limited to 16.5 kilobits per second and supportsonly low-resolution, low-frame-rate, black-and-whiteimagery. This link’s minimum 6-s control delay makesit unusable for real-time piloting and problematicfor payload control. The Ku-band SATCOM 1.544-megabit per second digital link supports 7 frames persecond of imagery and is the only link to supporttransmission of digital SAR data.

The GCS typically includes a dish antenna and aground data terminal (GDT) to support the C-bandLOS link; a Pilot Payload Operator (PPO) for air ve-hicle and payload control and viewing of imagery; anda Data Exploitation Mission Planning and Commu-nication (DEMPC) system used for mission planningand validation, data recording, and imagery processing.The Trojan Spirit II communications equipment maybe included to support the Ku-band data link. Figure1 shows the Predator UAV. Figure 2 depicts the normalconcept of operations using the GCS. The concept ofoperations for sharing the UAV between the GCS andthe SSN is described later in this article.

SSN-UAV SYSTEM CONCEPTAPL’s concept for the SSN-UAV system included

the following:

• Use of the C-band LOS as the communications linkbetween the SSN and the UAV.

Table 1. Major participants in the demonstration of submarine control of a UAV.

Organization Area of responsibility

ONI and N87 Demonstration sponsorsJPO for Cruise Missiles and UAVs Predator assetsSEAL Team One SOF team for operational demonstrationUSS Chicago (SSN 721) Submarine for demonstrationsUSS Coronado (AGF 11) Location of the JTFCAPL Technical Lead for development and testingGeneral Atomics Predator system (under contract to JPO)Naval Undersea Warfare Center SUB JDISS and interfaces to ship’s dataNaval Surface Warfare Center Installation of SSN antenna for UAV control

Note: JPO = Joint Program Office; JTFC = Joint Task Force Commander; N87 = SubmarineWarfare Division; ONI = Office of Naval Intelligence; SEAL = Sea, Air, Land; SOF = SpecialOperations Forces; SSN = fast-attack submarine; SUB JDISS = Submarine Joint DeployableIntelligence Support System; and UAV = Unmanned Aerial Vehicle.

ter cables from the radelectrical hull fitting for antennas to the inboardlow-noise amplifier was signal losses between the inboard electronics.

• Use of the GDT (from Geing of the proprietary LO

Table 2. Important characUAV.

Dimensions LenWi

Maximum altitude 25,Endurance 500

24 Sensors Ele

InfrSA

Navigation GPIne

Communication links C-bUHKu-

Antennas Omg

Dirg

Note: LOS = line of sight, GPSSAR = synthetic aperture radarmunications, and UHF = ultra-

• Use of C-band anten-nas (horn and flat-plate)mounted in a radomeon the AN/BRD-7 mastin place of thesubmarine’s AN/BRD-7 antenna. These C-band antennas weremounted on a pedestalthat provided antennapointing and motionstabilization. The SSN-UAV system is linkedto the UAV while thesubmarine is surfaced orat periscope depth withthe mast extended sothat the radome is abovewaterline.

• Use of low-loss radio fre-quency (RF) underwa-

ome to a modified ship’srouting of signals from the electronics. An outboardincluded to overcome themast-located antennas and

neral Atomics) for decod-S link into two channels of

teristics of the Predator

gth: 27 ftng span: 49 ft000 ft-nmi radius of operationsh on stationctro-opticalaredRSrtial navigationand LOSF SATCOMband SATCOMnidirectional (3 dB ofain)ectional horn (15 dB ofain)

= Global Positioning System,, SATCOM = satellite com-

high frequency.

V. VIGLIOTTI

real-time color video for imagery and one digitalchannel containing control and status data.

• Use of a subset of General Atomics’ ground controlPPO station for UAV and payload operation, statusand imagery viewing, and UAV data recording. Thissubmarine “mini-PPO” was functionally equivalentto the ground station PPO, except that the subma-rine PPO did not support actual UAV takeoff orlanding.

Figure 1. General Atomics Predator UAV.

504 JOH

• Use of additional computer equipment for interfac-ing to ship data, antenna pointing, and imageryselection, processing, reformatting, and transmittingto the SUB JDISS.

• Use of the SUB JDISS for data fusion and off-boardtransmission of imagery using the submarine UHFsatellite link.

This SSN-UAV system was designed to duplicate allGCS functions except takeoff and landing; that is, itwas designed to functionally replace the equipmentthat filled the 40-ft GCS trailer with equipment fittingon one torpedo room skid and to replace the 3-ft GCSdish antenna with a much smaller but equal or betterantenna that would fit into the space available on asubmarine mast.

Figure 3 shows the SSN-UAV system installed onthe Chicago. Figure 4 is a system block diagram. Asnoted earlier, the data link selected for the SSN-UAVsystem was the C-band RF LOS link. The C-band link,while suffering from LOS limitations, was the only linkto provide real-time piloting and two channels ofreal-time color video. The UHF link does not support

Figure 2. Predator concept of operations.

GlobalPositioning

System(GPS)

Ku-band Satellite Communications(SATCOM)

UHF Military SatelliteCommunications(MILSATCOM)

Commercial Satellite(COMSAT)

Air vehiclestatus andimagery

Mission updateand payload

controlAir tasking

order

Medium-altitudeendurance UAV

108-nmi(200-km)

line-of-sightdata link

Target area

Synthetic apertureradar (SAR) andelectro-opticaland infrared

Trojan Spirit IIJoint TaskForce C-II

UAV groundcontrol station (GCS)

Mission planning and controlLaunch and recovery

Unified andSpecified Commanders

National Military JointIntelligence Center

Joint ForceCommander

Joint IntelligenceCenter

Intelligence500 nmi(926 km)

Intel



real-time piloting and provides only a very slow updaterate for imagery. The Ku-band link provides flicker rate(seven frames per second) video and SAR data, butwas judged too risky since it was still under develop-ment during this demonstration.

The SSN 688 class submarine nominally has verylimited C-band receive capability and no C-bandtransmit capability. For this demonstration, C-bandreceive and transmit capability were added by replac-ing one of the submarine’s existing antennas (the

Sun workstationand displays

Pilot PayloadOperator (PPO)

stations

( )

SSN-UAV radome

AN/BRD-7 mast

(b)

Figure 3. Equipment for the SSN-UAV installed on USS Chicago.(a) Torpedo room equipment. (b) SSN-UAV radome mounted onAN/BRD-7 mast.

(a)

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1

AN/BRD-7) with a slightly modified commercial off-the-shelf antenna assembly housed in a custom ra-dome. Sea Tel provided the integrated stabilized an-tenna system (per APL specifications), consisting ofoutboard-located C-band flat-plate and horn anten-nas and stabilized pedestal assembly and an inboard-located pedestal controller. The narrow-beam (9°)high-gain (23.4-dB) flat-plate antenna was manufac-tured by Seavey Engineering Associates, and thewider-beam (30°) lower-gain (15-dB) horn is theduplicate of the Predator’s horn antenna. The flat-plate antenna served as the primary communicationslink and provided the maximum range between theSSN and the UAV. The horn served as a reduced-range backup or for short-range operations. The ped-estal provided a full 360° of azimuth coverage andelevation coverage (for both antennas) from –15° to105°. The 3-axis pedestal compensated for the roll,pitch, and yaw motions of the submarine. A trackballwas used for manual pointing of the antenna, but thenormal mode of operations was computer-controlledpointing using inputs of submarine heading and po-sition and UAV position. Pictures of the SSN-UAVantenna assembly are shown in Fig. 5, and a blockdiagram of the overall antenna RF system is given inFig. 6.

The SSN-UAV antenna assembly was housed in acustom radome. The major requirements for this ra-dome were (1) that it fit within the footprint of theAN/BRD-7 antenna, so that mast closure doors wouldnot have to be redesigned; (2) that it survive hydro-static pressures of 1000 psi; and (3) that it limit RFlosses through the radome at the frequencies of inter-est. APL specified detailed radome requirements andthen contracted with NURAD, who built the radomeusing cyanate ester with quartz fiber. Measured signallosses through the radome for the LOS C-band fre-quencies were less than 0.3 dB. NURAD also built theAPL-designed base plate, which mated to the AN/BRD-7 mast equipment.

A subset of General Atomics’ PPO console wasinstalled in the submarine’s torpedo room. This mini-PPO provided UAV and payload control (includingway point navigation and real-time piloting), waypoint mission planning, and display and recording ofUAV and payload status and imagery. Commercial andAPL-developed software operated on a Sun worksta-tion, also installed in the torpedo room, which sup-ported UAV image selection, enhancement, and refor-matting for SUB JDISS compatibility; transmission ofimagery to JDISS; communicating with the PPO forexchange of UAV and SSN data; and calculating andtransmitting antenna pointing information to thepedestal control unit. The submarine’s positionwas sent to the PPO for use in pointing the UAV’sdirectional horn antenna at the SSN.

998) 505

V. VIGLIOTTI

Submarine hull

UAV

AN/BRD-7 mast(C-band antennas)

Submarine controlroom equipment

UAV/payloadcontrol status

2 channelspayload imagery

Antenna positioncontrol and feedback

Control/statusand map data

Torpedoroom

equipment

Antenna pointingCommand and status

Real-time/playback

Payload imagery

GPSposition

data

Ship attitudeand

heading data

Still imagery

Status data

“Fused”imagery

AN/BRA-34 mast

GPS

SatelliteCommunications

Submarineradio room

SunworkstationMini-PPO

SUBJDISS

Pedestalcontrol

unit

GDTOfficer-of-the-deck

display

Figure 4. Functional block diagram of the SSN-UAV system. (GDT = ground data terminal, GPS = Global Positioning System, PPO =Pilot Payload Operator, SUB JDISS = Submarine Joint Deployable Intelligence Support System.)

Flat-plate antenna

( )

Horn antenna

Base plate

Figure 5. Antennas and pedestal subassembly for the SSN-UAV: (a) front view; (b) rear view. Flat-plate and horn antennas are mountedon a pedestal that provides motion compensation and azimuth and elevation pointing. The custom base plate mates to the submarine’sAN/BRD-7 mast.

(a) (b)

506 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1998)


Low-noiseamplifier

(+42.0 dB)

GD

T

Ship’s hull

Tx

Variableattenuator

Pedestal control/antenna select

10-ftcable

(–1.4 dB)

45-ftcable

(–6.3 dB)

5-ftcable

(–0.7 dB)Preamp

Variableattenuator

Final poweramplifier

(+41.7 dB)

(–1.5 dB)

Radome (–0.3 dB)

Diplexer(–1.2 dB)

Horn antenna(+15 dB)

Relay(–0.3 dB)

(+8.0 dB)

Flat-plate antenna(+23.9 dB)

AN

/BR

A-7

con

nect

or

Ped

esta

l ele

ctro

nics

EH

F c

onne

ctor

Rx

Low-noiseamplifier

(+42.0 dB)

Figure 6. Block diagram of outboard RF system with approximate component RF gains and losses. The signal is received and transmittedby either horn or flat-plate antenna (operator controlled via relay). The low-noise amplifier compensates for receive signal losses fromthe antenna to the ground data terminal (GDT). The variable attenuator is for adjusting the received signal at the GDT; both variableattenuator and preamplifier adjust the transmit signal. The final power amplifier compensates for transmit signal losses from the GDTto the antenna. (EHF = extremely high frequency.)

The SUB JDISS terminal, located in the subma-rine’s radio room, interfaced directly to the UAV real-time color video and received digital UAV images andpertinent submarine and UAV status data linked viaEthernet to the Sun workstation. SUB JDISS also hada direct connection to imagery collected with one ofthe submarine’s periscopes and was able to fuse thesedata with UAV data. The SUB JDISS terminal inter-faced with the ship’s UHF satellite communicationsequipment for off-board transmission of SSN-UAVdata.

SSN-UAV OPERATIONAL CONCEPTThe operational concept for SSN-UAV interoper-

ability is shown in Fig. 7. It includes the followingsteps:

• The submarine uses its own satellite communica-tions link to request UAV support and to providetime and geodetic location for transfer of UAVcontrol (“hand-off”) from the GCS located ashore tothe SSN.

• The GCS, located next to the airstrip, controls UAVduring takeoff and landing using LOS link.

• During transit to the designated location for thehand-off, the UAV is controlled by the GCS usingLOS, UHF, or Ku-band links. If SATCOM commu-nications links are used, then this distance may ap-proach 500 nmi. (Owing to unavailability of equip-ment and satellite time, the SSN-UAV demonstra-

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4

tion was limited strictly to LOS control of the UAV

by the GCS. This limited the hand-off location towithin 100 nmi of the GCS, the maximum LOS rangesupported by the GCS antenna system.)

• The submarine, operating at periscope depth withthe AN/BRD-7 mast extended, takes control of theUAV using the C-band LOS link and the establishedUAV hand-off procedures. Pilot and payload opera-tors in the submarine’s torpedo room then have fullcontrol of the UAV. Hand-offs and control of theUAV may be at nominal ranges of up to 85 nmi fromthe submarine’s position.

• Established loss-of-link and emergency hand-off pro-cedures are used where the submarine link is unin-tentionally or intentionally lost.

• Once the submarine’s UAV mission concludes, theUAV is flown under submarine control to the prede-termined location for hand-off to the GCS ashore.

• The GCS then takes control and returns the UAV toits operational base.

LAND-BASED AND AT-SEATECHNICAL TESTS OF THESSN-UAV SYSTEM

Before the at-sea exercise, a ground test of the SSN-UAV system was conducted at Fort Huachuca, Arizo-na. This test validated complete system functionalityand quantified the RF link performance. Also, thenewly developed normal and emergency hand-offprocedures of the air vehicle (from the GCS to theSSN-UAV system and from the SSN-UAV system to

(1998) 507

V. VIGLIOTTI

JTF/JIC

FLTSATCOM

UHF(32 kilobits per second)

Selected imagery

C–band LOSimagery/C 2

Range ≥ 86 nmi

Predator

Electro-optical/infrared

Figure 7. Concept for submarine interoperability with the Predator UAV (FLTSATCOM = Fleet satellite communications, JTF/JIC = JointTask Force/Joint Intelligence Center Commander).

the GCS) were tested. During this ground test, the airvehicle was flown, under control of the SSN-UAVequipment, out to a range of 92 nmi, which was thelimit of available airspace. Based on measurementstaken during the test, the maximum RF link range(maximum antenna gain configuration using SSN-UAV flat-plate antenna communicating with theUAV horn antenna) was estimated to be at least 145nmi, well above the 85-nmi requirement.

After the ground test, the SSN-UAV system wasinstalled on the Chicago for the at-sea technical andoperational demonstrations. During these at-sea exer-cises, the GCS ashore was located on San ClementeIsland near the runway used for UAV takeoffs andlandings, and the Chicago operated in the watersaround San Clemente. A SEAL (sea, air, land) NavySpecial Forces team embarked on the SSN to supportthe operational demonstration. The USS Coronado(AGF 11), underway in the Hawaii operating area3000 miles away, served as the location of the JTFCfor the operational exercise.

The technical tests at sea consisted of submarineoperations both at the surface and at periscopedepth. These tests primarily involved checks on basicSSN-UAV system functionality, including auto-matic and manual antenna tracking, switching of

508 JOH

SSN-UAV antennas, display of vehicle status andpayload information, control of payload sensors, waypoint mission planning and mission upload (to theUAV), real-time piloting, and tracking of stationaryand moving targets. Various quantitative performancechecks also were conducted to assess the quality of thereceived imagery, to measure the maximum ranges ofthe RF LOS link for the various SSN and UAV an-tenna combinations, and to assess the effects of SSNmaneuvering on the UAV data link. Significant re-sults of the at-sea technical tests are summarized asfollows:

• The SSN-UAV system was fully functional and dem-onstrated mission planning and way point naviga-tion, real-time piloting and control of UAV payload,and real-time viewing of UAV status (air vehicle andpayload) and UAV imagery. Real-time piloting wasnot part of the original system requirement.

• Numerous hand-offs of the UAV from the GCSashore to the SSN and from the SSN to the GCSwere successfully conducted, including hand-offs bothwith and without voice communications betweenthe pilot located on the SSN and the pilots locatedin the GCS. The tests also verified and exercisedemergency hand-offs and loss-of-link procedures.



• Periscope-depth submarine maneuvers or blockagesfrom other raised masts did not significantly degradethe SSN-UAV communications link.

• The measured RF link performance for all antennacombinations (UAV omnidirectional antenna, UAVhorn antenna, SSN-UAV flat-plate antenna, andSSN-UAV horn antenna) significantly exceededdesign requirements. The SSN-UAV antenna sys-tem consistently provided better imagery, at signifi-cantly greater ranges, than did the GCS antennasystem ashore (GCS to UAV ranges nominally lim-ited to approximately 100 nmi for LOS link control).

• During long-range testing, the UAV was flown out to104 nmi under control of the SSN. This demon-strated maximum range was bounded by exerciseconstraints, not by SSN antenna performance. Theselong-range tests indicated that the SSN-UAV datalink in the maximum gain configuration (SSN-UAVflat-plate antenna communicating with UAV hornantenna) was not limited by RF design, but rather bythe radio horizon. This radio horizon corresponds toa maximum data link range of approximately 170nmi for a submarine at periscope depth and a UAVoperating at 20,000 ft (Spangler3)—well in excess ofthe 85-nmi system requirement. In fact, the SSN-UAV RF link was still functional at 100 nmi usingthe lower-gain SSN-UAV horn antenna.

In summary, the technical tests during the at-sea dem-onstration validated that the SSN-UAV system met orexceeded all requirements.

SSN-UAV OPERATIONALDEMONSTRATION

JDISS

USS Corona

Figure 8. Imagery diFleet satellite, GCSSupport System.)

The overall scenario for theoperational demonstration devel-oped by N87 was described byRear Admiral Jones in an April1995 letter:

U.S. surveillance in a vital littoralregion is stepped up in response tothreats from a hostile country toclose off a strategic strait whichcontrols access to the region. AnSSN is operating in the littoralregion with a Special OperationsForces (SOF) contingent em-barked. Predator UAVs, flying froman adjacent friendly country, areproviding near-continuous surveil-lance of a strategic island in thestrait. A Joint Task Force consistingof a Carrier Battle Group and aMarine Amphibious Group issteaming toward the strait to pro-tect merchant traffic entering andexiting the littoral region. The

JOHNS HOPKINS APL TECHNICAL DIGEST, V

Carrier’s strike aircraft will not be in range of the strait foranother 24 hours.

For the purposes of this demonstration, the littoralregion was the waters off of San Clemente Island, andthe friendly country and strategic island were differentlocations on that Island.

The actual events of the operational demonstrationwere as follows:

• The Chicago conducted an all-sensor search off the“hostile coast” using the submarine’s electronic sur-veillance equipment and simulated the detection ofhostile forces’ RF transmissions from a mobile missilesite.

• The SSN then requested (from the JTFC) use of aPredator UAV to conduct surveillance and recon-naissance for SOF mission planning. This requestwas granted; a Predator was launched using the GCSashore and then handed off to the SSN.

• The SSN took control of the UAV and used it tolocate the missile site. Predator video clips were fusedwith the simulated electronic surveillance informa-tion, and annotated imagery was transmitted viaSUB JDISS and the ship’s satellite communicationsequipment to the JTFC embarked on the Coronado.The imagery dissemination path is shown in Fig. 8.The SOF tactical commander, stationed on the SSN,also used the UAV for detailed surveillance of thecoastline, selection of beach landing sites and routesto target, and monitoring of the disposition of hostileforces.

• The JTFC ordered the SSN to conduct an SOFmission to destroy the missile launcher site (use laser

FLTSAT

do

Predator

USS Chicago

JDISS Mini-GCS

ssemination path during the operational demonstration. (FLTSAT = = ground control station, JDISS = Joint Deployable Intelligence

OLUME 19, NUMBER 4 (1998) 509

V. VIGLIOTTI

to illuminate target to support an air strike usinglaser-guided munitions).

• During nighttime operations, the SSN used the UAVto conduct maritime surveillance to verify that thearea was clear before surfacing. The SSN surfaced,the SOF team was launched, and the SSN thensubmerged to periscope depth and remained in con-trol of the UAV. Radio communications were main-tained between the SEAL team tactical commander,located on the submarine, and the embarked SOFteam.

• The SEAL team tactical commander used UAVinfrared imagery to monitor SOF team ingress. Aninterfering contact (a private yacht moored off SanClemente Island) was observed on the UAV imag-ery, and the SEALs were directed to an alternatelanding site. After landing, the SEAL team wasunable to reach the target area on the first night andremained concealed during the following day.

• During the following day, hostile forces repositionedand hid the mobile missile and launcher. The SSNused the UAV to locate the hidden target and torelay target movements to the SEAL team. Subma-rine operators then observed the missile being movedonce again and saw that preparations were beingmade for missile launch. Selected imagery showingthe missile in launch position was transmitted to theJTFC. The JTFC ordered a precision strike againstthe target, with the SOF team using a laser to desig-nate the target.

• The target was destroyed (an air strike was simulatedby detonating charges around the mobile missile).The SOF commander onboard the SSN monitoredthe strike and assessed battle damage in real time. Theassessment was relayed to JTFC in near real time.

• The SOF commander used the UAV to aid theSOF team’s egress by monitoring reaction of hostileforces.

Figure 9 shows highlights from the operational dem-onstration.

This operational exercise conducted with the Chi-cago and the Predator UAV conclusively demonstratedthat an SSN can employ UAVs for real-time tacticalintelligence. Furthermore, employment of a UAV canadd significant capability to a variety of submarinemissions. It can add precision target location andsurveillance, reconnaissance for real-time SOF missionplanning, relay of real-time intelligence to a deployedSEAL team, real-time situational awareness for theSEAL team commander deployed on the SSN, andreal-time battle damage assessment. An importantresult for the SSN and UAV Concept of Operationsderived from this demonstration was that the on-scenetactical commander must have direct real-time controlof the UAV.

510 JOH

SUMMARYThe Laboratory successfully planned and completed

the first-ever demonstration of interoperability be-tween a UAV (Predator) and a submarine (Chicago).This task was accomplished in 10 months, and allrequirements for the demonstration were met or ex-ceeded. The effort included development of a mast-mounted low-loss radome housing a size-limited, mo-tion-compensated steerable C-band antenna withsufficient gain to achieve data link ranges in excess of100 nmi; an RF system design using low-noise ampli-fiers and low-loss cables to account for signal lossesassociated with the submarine installation; smallerUAV control consoles compatible with a torpedo roominstallation; and procedures for transferring UAV con-trol between the GCS and a moving SSN. During thedemonstration, UAV pilots aboard the SSN, sub-merged (at periscope depth), took control of both thePredator and its sensor payload and used the UAV tosupport an SOF team that had embarked from the SSNand headed ashore to help destroy a simulated mobileland-based missile site. The SOF team commander,located on the SSN, used real-time data and imageryfrom the UAV for reconnaissance of potential beachlanding sites and land routes to the target; for mon-itoring of the location, movements and readiness (forlaunch) of the mobile missile; for real-time battle dam-age assessment; and for observing the SOF team ingressand egress and the location and reaction of hostileforces. In addition, selected UAV imagery was trans-mitted in near real time via satellite to the JTFClocated 3000 miles away.

This type of demonstration showcases APL’s capa-bility for responding quickly to sponsor requirementsto design, develop, and deploy operational systems thatwork, and work well, the first time. This message fromRear Admiral E. P. Giambastiani (N87) was receivedin July 1996 after the test:

Congratulations to the crew of USS Chicago, SEAL TeamOne and the Johns Hopkins University Applied PhysicsLaboratory for the extremely successful completion of theSSN-Predator Unmanned Aerial Vehicle Demonstration.The recent at-sea demonstration of a submarine’s ability tofly a Predator UAV and control its payloads in support ofa special warfare exercise is unprecedented in the historyof the submarine force and the United States Navy.

REFERENCES1Rau, J. L., Spangler, R. W., Ball, R. E., and Vigliotti, V., SSN-UAV

Demonstration, a White Paper Presenting the Proposal for a Near-TermDemonstration of SSN and UAV Coordinated Operations, JHU/APL, Laurel,MD (Nov 1994).

2Unmanned Aerial Vehicles (UAVs) 1995 Annual Report, Defense AirborneReconnaissance Office, Washington, DC (Aug 1995).

3Spangler, R. W., San Clemente Island (SCI) UAV/SSN Long Distance TestResults, Report SSD/PM-96-034, JHU/APL, Laurel, MD (Jun 1996).



Altitude = 12,500 ft, slant range = 2.5 nmi

(a)

(b)

Altitude = 12,500 ftSlant range = 2.5 nmi

Altitude = 8,500 ftSlant range = 3.0 nmi

(c)



(d)


(e)

IR imageryAltitude = 8,600 ftSlant range = 3.5 nmi

IR imageryAltitude = 8,600 ftSlant range = 1.5 nmi

(f)

Figure 9. Highlights of the operational demonstration, showing the UAV under control of submarine operators and UAV imagery viewedin real time by the SOF team commander located on the submarine. UAV imagery also was transmitted in near real time (via satellite)to the JTFC, who was 3000 miles away. (a) SEAL team practicing deployment (submarine periscope image). (b) UAV used to locate andimage the hidden threat missile system. (c) After the threat missile is moved, the UAV again locates it. (d) UAV tracks repositioning oftarget. (e) UAV images the “ready-to-launch” missile. (f) UAV images are used by SOF commander for real-time viewing of targetdestruction and for battle damage assessment.

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1998) 511

V. VIGLIOTTI

THE AUTHOR

VINCENT VIGLIOTTI is a member of APL’s Principal Professional Staff. Hereceived a B.S. degree in physics from Fairfield University, an M.S. degree inphysical oceanography from the University of Michigan, and an M.S. degree incomputer science from The Johns Hopkins University. He worked for the NavalOceanographic Office for 2 years as an oceanographer before joining APL’sStrategic Systems Department in 1980. At APL, Mr. Vigliotti has participatedin all facets of oceanographic data collection systems development anddeployment. In 1990, he was appointed the Program Manager of the OceanData Acquisition Program. His e-mail address is [email protected].

512 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 19, NUMBER 4 (1998)

mailto:[email protected]

Documents

Demonstration of Submarine Control of an Unmanned Aerial Vehicle