From: Walter Daniel <75066.164@compuserve.com>
Subject: DARPA Microsat results
Apparently-To: sci-space-news@ames.arc.nasa.gov
Followup-To: sci.space
Originator: yee@atlas.arc.nasa.gov
Organization: United States Naval Academy, Annapolis, Maryland
Date: Sat, 7 Nov 1992 07:24:10 GMT

[This file contains the text and figure captions of two conference 
papers detailing demonstrations of the DARPA Microsats, seven small UHF 
communications satellites.  Please distribute this file to any computer 
network or BBS that is appropriate.  Due to the length and content of 
this file, it is NOT suitable for the amateur packet radio network.]
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NAVY/MARINE CORPS DEMONSTRATIONS OF THE DARPA MICROSATS

Walter K. Daniel
United States Naval Academy
Annapolis, Maryland

Robert E. Bruninga
Bendix Field Engineering Company
Annapolis, Maryland

presented at the Sixth Annual Conference on Small Satellites
Utah State University, Logan, Utah
September 21-24, 1992

Abstract

Demonstrations of the DARPA Microsats with an emphasis on Navy and 
Marine Corps applications were conducted by personnel at the United 
States Naval Academy.  These satellite communications demonstrations 
used the analog FM mode of the Microsats.  Radios used were military 
transceivers, transmitters composed of laboratory signal generators with 
broadband power amplifiers, a modified amateur radio UHF transmitter, 
and commercially-available scanner receivers.  Voice demonstrations 
included equipment checks with DARPA personnel, a tactical exercise at a 
Marine Corps base, and communications with a U.S. Navy destroyer.  
Position and status report data beacons were relayed through the 
Microsats from training vessels to Annapolis.  Satellite-to-satellite 
communications using the Microsats and a U.S. Navy FLTSAT were 
successfully conducted.

Introduction

The DARPA Microsats were launched on the second Pegasus mission during 
July 1991 into 245 nm by 192 nm initial orbits [1].  (The satellites 
reentered the atmosphere and were destroyed during late January 1992.)  
These seven small spacecraft included both analog FM transponders and 
digital store-and-forward capability for operation in the military UHF 
spectrum of 225-400 MHz.  The uplink and downlink frequencies were 
offset by 41 MHz during voice operations.

Personnel at the United States Naval Academy took part in the 
demonstrations of the Microsats with an emphasis on Navy and Marine 
Corps applications.  Naval Academy facilities such as the Satellite 
Earth Station Facility, the 12-meter parabolic dish antenna, and 
training vessels were used.  Note that frequencies described in this 
paper are approximate, not exact.

Equipment

The Microsat transponders were designed to be compatible with existing 
military UHF transceivers [2].  Units such as the AN/PSC-3A and AN/LST-5 
could have been used, but such radios were not widely available.  DARPA 
did loan equipment to the Academy for specific demonstrations; no other 
source for military equipment was found.

For day-to-day monitoring of the Microsat downlinks, commercially-
available scanner receivers were used.  Many of these frequency-
synthesized receivers have the military UHF frequencies locked out by 
the microprocessor, but two units marketed by Ace Communications did 
not.  The AR3000 is a multi-mode tabletop scanner that is tunable in 1 
kHz increments, a feature that was used for tracking the severe Doppler 
shift of the Microsat downlinks.  The AR1000XC is a handheld battery-
powered scanner that was used for portable operations.  Narrow-band FM 
mode (12.5 kHz IF filter) was used with the Microsats.  The military 
radios have 25 kHz IF filters, so those units were not affected by the 
+/-7 kHz Doppler shift caused by the velocity of the low orbit.

When operating from a fixed location or vessel, Academy personnel used 
laboratory signal generators and broadband power amplifiers configured 
as FM transmitters.  A voice or data signal was used to frequency 
modulate a 260 MHz carrier in the signal generator, then the output was 
magnified to approximately 5 watts RF by the power amplifier.  For voice 
operations, a microphone signal was preamplified by a cassette recorder 
before being routed into the signal generator.  For data operations, the 
audio output of the data device was connected directly into the 
modulation input of the signal generator.  Figure 1 is a photograph of a 
signal generator and AR3000 receiver being used for Microsat operations.

A battery-powered portable transmitter for use with the Microsats was 
adapted from an amateur radio kit.  The Hamtronics TA451 UHF FM exciter 
is designed for the amateur band at 440 MHz, but crystals for 260 MHz 
were installed on the circuit board and tunable circuits were redesigned 
for military UHF operation.  The transmitter was powered by several 
consumer-grade AA alkaline batteries and provided 2 watts RF power, 
sufficient for the low-altitude Microsats.

A variety of antennas were used with the Microsats.  The downlink 
signals were strong enough that simple whip and discone antennas were 
usually sufficient.  A circularly-polarized crossed dipole antenna was 
installed at the Naval Academy for day-to-day use; the circular 
polarization prevented signal fading during a satellite pass.  A 
portable crossed-dipole manufactured by Dorn-Margolin for military use 
was borrowed from DARPA along with the AN/PSC-3A transceiver.  An 
antenna similar to the Dorn-Margolin model was fabricated at the Naval 
Academy using metal mini-blind slats.

The only data device used in Naval Academy demonstrations was the 
Kantronics All Mode (KAM) terminal node controller (TNC) that is sold to 
the amateur radio market.  The KAM can operate on both HF and VHF/UHF 
frequencies.  A system of KAMs already installed on Naval Academy 
training vessels for HF communications was easily adapted for use with 
military UHF frequencies.

Two satellite tracking programs used by amateur satellite trackers were 
used for the Microsat demonstrations.  OrbiTrack for the Apple Macintosh 
by BEK Developers was used to predict future passes in great detail.  
InstanTrak for MS-DOS machines was used in the Naval Academy satellite 
facility during Microsat passes to calculate Doppler shift and satellite 
elevation.  NORAD satellite elements were distributed by T. Kelso of the 
Air Force Institute of Technology via the Internet on a weekly basis, so 
the satellites were accurately tracked until reentry.

Demonstrations

Immediately after the satellites were launched and orbital elements 
became available in early August 1991, Naval Academy personnel began 
monitoring the downlink frequencies using the AR3000 scanner receivers.  
The signals were strong and initial voice tests were clear and legible.  
As soon as a voice transmitter composed of a signal generator and power 
amplifier was assembled, the Naval Academy joined the early Microsat 
nets that also included stations at Quantico, Virginia and Fort Gordon 
in Georgia.

The HF position reporting system being used by Naval Academy training 
vessels was adapted to Microsat operations in August 1991.  The VHF 
audio output of the KAM TNCs was connected to a signal generator/power 
amplifier transmitter and routed to an external UHF antenna.  Watch 
personnel on the vessels typed updated position and status reports on a 
computer terminal that was connected to the KAM.  The KAM was set to 
beacon the position report every minute.  When a Microsat in analog FM 
mode came into view, the satellite would receive and retransmit the 
beacon.  An AR3000 receiver connected to a KAM received the reports in 
Annapolis; the reports were both stored in memory and printed on paper.  
On 16 August 1991, the Naval Academy received the beacon "NS-4>
T1600/L395056/G0751807/C272/S11/F63/W100/LO99/MSD20/ALL OK/NS-4" from a 
training vessel near Philadelphia.  The latitude and longitude place  
NS-4 in the shipping channel near the Philadelphia airport.  An amateur 
radio operator in Massachusetts received the beacons using similar 
equipment.  For example, the operator received the text "ACADMY-1>
LOG>BEACON: US Naval Academy MICROSAT TEST Lat:38 59 Long 76 29" on 20 
November 1991.

In mid-September 1991, personnel from the Naval Space Command organized 
a demonstration using AN/PSC-3 transceivers and Dorn-Margolin antennas.  
One station was set up on the roof of a building in Dahlgren, Virginia 
while the other station was set up on board one of the Naval Academy 
training vessels (see Figure 2).  At the beginning of the first 
satellite pass, the vessel was under way in the Chesapeake Bay near 
Annapolis.  The two stations exchanged voice communications without 
difficulty.  The satellite downlink was monitored ashore at the Naval 
Academy and the signals from both stations were clear and 
understandable.

In mid-November 1991, a tactical satellite communications exercise 
utilizing the Microsats was conducted by midshipmen and faculty at the 
Quantico Marine Corps Base in Virginia.  For nearly one hour, two groups 
of midshipmen were able to communicate with each other and with a 
station at the Naval Academy.  Amateur radio operators and scanner 
enthusiasts in the eastern United States and Canada monitored the 
satellite transmissions.  This exercise is detailed in an accompanying 
paper [3].

During December 1991, a demonstration was conducted with the USS Arleigh 
Burke, the first Aegis-class destroyer.  The Burke was at the U.S. Navy 
base in Norfolk, Virginia.  An officer on the Burke configured the 
existing WSC-3 UHF radio on the ship for satellite use.  Although not 
all the settings were made correctly (the radio was probably left in AM 
mode when it should have been in FM mode), the following hour-long 
exercise provided communications that were understandable.  For example, 
the officer on the Burke read a telephone number to the Naval Academy 
and the number was copied correctly.  During the demonstration, one of 
the DARPA support contractors joined the net by transmitting from a 
vehicle in northern Virginia using an AN/PSC-3A and Dorn-Margolin 
antenna.  An amateur radio operator in Massachusetts monitored the 
transmissions from all three stations by using a commercial scanner 
receiver and discone antenna.

One of the original goals of the Microsat program was to demonstrate 
satellite-to-satellite communications.  This goal was achieved during a 
December 1991 test conducted by personnel at the Naval Academy and by 
DARPA contractors located in northern Virginia.  The Microsat 
transponders had an uplink frequency 41 MHz below the downlink 
frequency; the U.S. Navy FLTSATCOM transponders also have 41 MHz 
offsets, but  the uplink is above the downlink frequency.  The Microsat 
transponders were tuned to a FLTSATCOM channel frequency so that the 
geostationary satellite could relay the Microsat transmissions over a 
much larger area (see Figure 3).  During the demonstration, two stations 
in northern Virginia communicated through the Microsats while personnel 
at the Naval Academy monitored the FLTSATCOM downlink using a 12-meter 
parabolic dish antenna.  The voice communications were clear and 
understandable in both the Microsat and FLTSAT downlinks.

The success of amateur radio operators monitoring the Microsats prompted 
an effort to organize a wide-area network of stations.  Naval Academy 
personnel received permission to publicize the effort through the 
Military Affiliated Radio System (MARS) that usually passes messages for 
military personnel by HF radio nets.  Bulletins regarding the 
demonstration were circulated through amateur radio networks as well.  
During some of these nets, stations all over the United States checked 
in; two ships at sea participated at various points.  While the tests 
took place when the satellites were about to decay from orbit, clear and 
understandable contacts were made by participants with varying types of 
equipment.

Conclusions

Numerous Navy and Marine Corps demonstrations of low Earth orbit UHF 
communications were conducted at the Naval Academy.  Military 
transceivers, commercially-available equipment, and experimental gear 
was used.  These demonstrations indicate the ability of low Earth orbit 
satellites to provide additional communications paths for units on the 
ground or at sea.

References

1.  R. Bonometti, E. Nicastri, T. Darone, R. Steele, and W. Montag, 
"Application of Small Satellites for Defense Space Communication Systems 
and Technology Development," Fifth Annual AIAA/USU Conference on Small 
Satellites, Logan, Utah, August 1991 

2.  "Technical Operations Guide for Users, DARPA Advanced Space 
Technology Program, Lightsat Communications Demonstration," Defense 
Advanced Research Projects Agency, Arlington, Virginia, February 1990

3.  W. K. Daniel, G. Rivas, and R. E. Bruninga, "Marine Corps Tactical 
Satellite Communications," Sixth Annual AIAA/USU Conference on Small 
Satellites, Logan, Utah, September 1992

Acknowledgements

In addition to the individuals who monitored the Quantico demonstration 
(see list in accompanying paper), the authors wish to thank John Biro 
for monitoring the packet beacons as well as recording the exercise with 
the USS Arleigh Burke.

Figure 1.  Signal Generator Transmitter and AR3000 Scanner Receiver
Figure 2.  Microsat Antenna Being Installed on Training Vessel
Figure 3.  Microsat-to-FLTSAT Relay
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MARINE CORPS TACTICAL SATELLITE COMMUNICATIONS

Walter K. Daniel
United States Naval Academy
Annapolis, Maryland

Gavino Rivas
Second Lieutenant
United States Marine Corps

Robert E. Bruninga
Bendix Field Engineering Company
Annapolis, Maryland

presented at the Sixth Annual Conference on Small Satellites
Utah State University, Logan, Utah
September 21-24, 1992

Abstract

A tactical satellite communications exercise using the DARPA Microsats 
was conducted by Naval Academy personnel at the Quantico Marine Corps 
Base in Virginia.  Midshipmen used a military UHF radio, a modified 
amateur radio transmitter, and scanner receivers while a station in 
Annapolis communicated with them.  Voice communications were clear and 
understandable even when the tactical teams were in the woods.  Amateur 
radio operators and scanner enthusiasts around the eastern half of the 
United States and Canada successfully monitored the Microsat downlinks 
during the demonstration.

Introduction

In the United States Marine Corps concept of maneuver warfare, 
communication plays a key role.  The Corps doctrine manual states that 
"...key people~'actuals'~should talk directly to one another when 
possible, rather than through communicators or messengers...[they] 
should communicate orally when possible, because we communicate also in 
how we talk; our inflections and tone of voice" [1].  Small satellites 
in low Earth orbit can provide voice channels to tactical units deployed 
over large areas; these channels enhance the communications that are 
required for maneuver warfare.  A low Earth orbit allows the use of low-
power transmitters and simple antennas that are small and lightweight.  
Low power transmissions are difficult to locate, so the risk of exposing 
positions by communicating is greatly reduced.

During November 1991, midshipmen, faculty, and staff of the United 
States Naval Academy conducted a tactical satellite communications 
demonstration using the seven DARPA Microsats.  Tactical units at the 
Quantico Marine Corps Base in Virginia communicated with a command 
station in Annapolis and with each other.  The goal of the demonstration 
was to show that the Microsats could provide high quality voice 
communications that would satisfy requirements as stated in Marine Corps 
doctrine.

Equipment

The radios and antennas used in this demonstration are detailed in a 
companion paper [2].  An AN/PSC-3A transceiver with Dorn-Margolin 
antenna was the primary station in the field at Quantico.  The modified 
Hamtronics transmitter, an AR1000XC scanner receiver, and a mini-blind 
crossed dipole antenna was the secondary station at Quantico.  An 
AR1000XC receiver with mini-blind antenna was used as a receive-only 
station while another AR1000XC with discone antenna was used for 
monitoring the progress of the exercise.  The Naval Academy station used 
a signal generator/power amplifier transmitter and an AR3000 receiver 
with a roof-mounted crossed-dipole antenna.

Demonstration Procedure

Before the first satellite pass, the participants and radios were 
gathered in the center of a helicopter landing zone at Quantico.  The 
midshipmen were assigned in teams of four or five to the AN/PSC-3A, 
Hamtronics, and receive-only stations.  During the first satellite pass, 
each rig was used to establish contact with the Naval Academy for final 
checkout, then the team assigned to that rig moved into the woods 
surrounding the landing zone.  The two teams with transmitters 
maintained contact with the Naval Academy and with each other through 
the Microsats while the receive-only team monitored the downlink.  
Sample status reports that were prepared in advance were read over the 
satellite channel to test legibility of the signals.

Demonstration Performance

Shortly after the predicted appearance of the first satellite, a call 
from Quantico to the Naval Academy with the AN/PSC-3A (see Figure 1) was 
promptly answered.  The Hamtronics transmitter (see Figure 2) also 
worked well during checkout.  With all equipment verified as functional, 
the three teams began moving in different directions.  The receive-only 
team immediately entered the woods and monitored the downlink for the 
duration of the exercise.  The two transmitters moved initially to the 
edge of the woods, then as far as 100 meters into the woods to test 
signal loss due to vegetation.

Throughout the exercise, voice communications were clear and 
understandable.  Both transmitters at Quantico and the one at the Naval 
Academy had sufficient power to be full quieting in the Microsat 
receivers.  Communications were maintained almost continuously for 52 
minutes.  While there were still some leaves on the trees, signal loss 
due to vegetation was not noticeable for any station.

Ground Tracks

Tracking programs were used to examine timing and elevation of each 
satellite pass of the demonstration.  The satellites moved from North to 
South over the eastern United States during late afternoon on 16 
November 1991.  The first satellite, Microsat 7, had a peak elevation of 
37 degrees above the horizon to the east.  The following satellites 
appeared at higher peak elevations to the east,  then lower elevations 
to the west.  The last satellite, Microsat 1, had a peak elevation of 31 
degrees to the west.  The satellites were almost evenly spaced, so near-
continuous communications were possible.  Figure 3 shows the positions 
of the satellites and their footprints early in the exercise, shortly 
after Microsats 7 and 3 have passed Quantico.  Figure 4 shows the 
positions of the satellites near the end of the exercise as the last 
satellite is about to pass to the west of Quantico.

Monitoring Stations

Two days before the exercise, Naval Academy faculty sent Internet 
computer bulletins describing the upcoming demonstration and inviting 
amateur radio operators and scanner enthusiasts to monitor the downlink.  
Reception reports were requested to be sent by Internet electronic mail.  
A total of 12 individuals responded.  Their locations (see Figure 5) 
included North Carolina, Virginia, Maryland, New York, Massachusetts, 
New Hampshire, Ontario (Canada), New Brunswick (Canada), Ohio, and 
Minnesota.  The station in Minnesota was the most distant at 
approximately 900 statute miles.  While they reported varying amounts of 
legibility (caused largely by variations in receivers and antennas), 
many of these individuals accurately reported samples of the 
transmissions that took place.

Conclusions

The Microsat demonstration at Quantico proved that tactical satellite 
communications using low-Earth orbiting spacecraft is feasible.  Small 
radios and non-directional antennas simplify procedures for the units in 
the field.  Spacecraft like the DARPA Microsats can provide the kind of 
clear voice communications that the Marine Corps requires for maneuver 
warfare.

References

1.  Warfighting, FMFM 1, United States Marine Corps, 1989.  The emphasis 
is in the original document.

2.  W. K. Daniel and R. E. Bruninga, "Navy/Marine Corps Demonstrations 
of the DARPA Microsats," Sixth Annual AIAA/USU Conference on Small 
Satellites, Logan, Utah, September 1992

Acknowledgements

The authors wish to thank the individuals who took the time to monitor 
the Microsat downlink during the exercise and send reception reports.  
This group includes Lee Reynolds of Greenville, NH; Bill Jones of 
Churchville, MD; David Wilson AC4IU of Fredericksburg, VA; Richard 
Langley of Fredericton, New Brunswick, Canada; Bruce Frederick KA1FGY of 
Burlington, MA; Marvin Hoffman KD4EGV of Boone, NC; Chris Elmquist N0JCF 
of St. Paul, MN; Tom Evert of Akron, OH; Bob Lyle of Milton, Ontario, 
Canada; Bob Scott of Alexandria, VA; Dwight Smith N2FMC of Chappaqua, 
NY; and Brian McCarthy NX9O of Binghamton, NY.  73 de N3KVQ & WB4APR!

Figure 1.  Operation of AN/PSC-3A Transceiver
Figure 2.  Operation of Handheld Transmitter/Receiver
Figure 3.  Satellite Positions Early in Demonstration
Figure 4.  Satellite Positions Late in Demonstration
Figure 5.  Locations of Monitoring Stations
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[Please note that due to a complete lack of support from DARPA and the 
Naval Academy, I had to write these papers on my own time and attend the 
conference at my own expense.  I simply do not have the resources to 
mail dozens of copies of the papers or answer hundreds of questions 
about the demonstrations.  I am no longer employed at the Naval Academy, 
so please do not try to contact me there.

I can mail a limited number of copies of the paper for those who wish to 
see the figures.  Send me a self-addressed envelope (9 inches by 12 
inches if you don't want the papers folded) with 98 cents postage to 
Walter Daniel, 1506 Hickory Wood Dr, Annapolis, MD  21401 before 1 June 
1993.  I will only send the papers to US addresses.

The Microsats reentered the atmosphere and were destroyed during January 
1992, so there will be no more demonstrations.  I will not give out the 
exact frequencies that were used.  I am no longer employed at the Naval 
Academy, so I will not be involved with future DARPA satellite projects.  
There are currently no functioning US military communications satellites 
in low Earth orbit, so there is nothing to monitor.  If you want more 
information about FLTSAT, I'dd suggest that you check Larry van Horn's 
book on communications satellites.

If you work for the US military or US industry, you may wish to contact 
DARPA directly.  The DARPA support contractor with responsibility for 
the Microsat demonstrations is Space Applications Corp, 4001 N Fairfax 
Dr, Suite 250, Arlington, VA  22203.

Here are email addresses.  Please keep in mind that I am working alone, 
on my own time, and at my own expense.  Thanks!

Walter Daniel N3KVQ
Internet:  n3kvq@@amsat.org
CompuServe:  75066,164
Packet radio:  n3kvq@@ka3rfe.md.usa.noam]
Newsgroups: sci.space.news