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ECHO Operations Planning

WAVE Mode for Operating the ECHO Satellite                 18 Oct 2003

ECHO will launch this year and carry a tremendous capability and
flexibility for communications experiments in the Amateur Satellite
Service.  With 5 user receivers and 3 downlink transmitters almost any
communications mode can be supported.  The problem is, how to share the
numerous modes and configuration possibilities so that most of the
thousands of potential users are generally satisfied.  Having too many
conflicting modes, and complex operating schedules actually detracts from
the optimum satisfaction by the general cross-section of users.

This paper has no official basis with AMSAT nor the ECHO design team and
is offered only as a draft-strawman to serve as a target for discussion by
the AMSAT community as to how it will operate AMSAT ECHO.  There are three
primary recommendations:

1) AMSAT should designate an ECHO Operations Committee who will manage the
day-to-day operation of the spacecraft to best serve users.

2) AMSAT should publish a clear USER SERVICE AGREEMENT that specifically
defines the rules, limitations, recommendations and requirements for users
to use the spacecraft.

3) The default operating mode should generally be optimized to satisfy the
largest cross-section of users while balancing simplicity with complexity
and easy use with experimental modes.

These points will be addressed in reverse order.

To minimize frequent mode changes and to provide the most users with
something they can use most of the time, this paper proposes a nominal
initial operating configuration.  Other experiments may be conducted
periodically and other modes developed as software matures, but we need to
start somewhere.  The basis for this approach is the consideration that
for maximum utility in education, student and new operator outreach,
common modes must be available on a routine basis most of the time.
Therefore the following default operating mode is proposed for the 5
uplink receivers.  It is called WAVE for its primary modes:

---- --- -------------------------- ----------  -----------
 W   RX1 WISP Multiuser File System 145.xxx     4W 435.xxx
 A   RX2 WISP and APRS shared       145.yyy     (shared with above)
 V   RX3 Voice FM (PL enabled)      145.zzz     8W 435.zzz
 E   RX4 Experimental
 -       (HF) Multiuser             29.400      S-Band WFM
         (LV) Lband Voice           12xx.xxx    S-Band WFM
         (LB) Lband Bent Pipe       12xx.xxx    S-Band WFM
         (LD) Lband digital         12xx.xxx    S-Band Digital

Key factors involved in this arrangement are:

WISP:  A continuation of the very successful file store and forward system
use by all of the previous PACSATS.  With two uplinks (RX1 and RX2), user
contention is shared for improved uplink throughput.  Distribution of
files, news and bulletins will be via this system.  The default baudrate
is 9600 baud.  This system will best serve mobile portable and remote
travelers by giving them remote communications access via SATgates back to
the internet.  I'd rather see 9600 baud used to give solid reliability to
simple users with OMNI antennas most of the time, rather than giving
higher speed but then requiring tracking.

APRS:  APRS mode simply represents the enabling of UI digipeating of UI
packets to be merged into the 9600 baud digital downlink.  Enabling of UI
digipeating as a shared mode with the PACSATS has a legacy that includes
AO-16, UO-22 and IO-26.  UI digipeating users are constrained to only
uplink on Receiver RX2 to minimize contention with the WISP system.  UI
digipeating is fully compatible with the Kenwood TM-D700 and TH-D7 Mobile
and Handheld APRS radios with only whip antennas.  APRS I-gates feed all
UI packets heard on the downlink into the worldwide APRS internet system.

VOICE:  FM Voice relay (EZ-Sat) continues the legacy of UO-14, AO-27,
SUNSAT, SO-50 and others to support the most popular AMSAT mode which can
be received by any user with an FM HT.  Voice and SSTV may share this mode
when suitable nets are scheduled to support special events.

EXPERIMENTAL: Because of the very high doppler and short duration passes,
the S-Band downlink will use Wideband FM compatible with any FM broadcast
band receiver as the nominal mode for this transmitter.  Using 75 KHz
deviation, Only minor Doppler adjustment twice or so per pass is required.
Nominal AO-40 S-Band receive systems feeding any FM system set to Wideband
FM should work well for the downlink.  Several experimental uplinks are

(HF) HF (CW,SSTV,PSK-31) - The preferred default for the experimental RX4
receiver should be a 10m HF uplink which can contain dozens of
simultaneous users including CW, SSTV and PSK-31.  By tuning the HF
receiver to 29.400, an entire 3 KHz of HF spectrum can be relayed full
duplex in the wideband FM downlink.  This is Identical to the HF
transponder on PCSAT2. In this 3 KHz of audio, the lower 800 Hz can be
multiple narrowband CW users, 800 to 2000 Hz is available for SSTV, and
2000 to 3000 Hz is dedicated to PSK-31 users.  This downlink can be
received, demodulated and displayed by anyone with an S-Band
downconverter, a broadcast band WFM receiver and soundcard DSP software.

(LV) L-BAND VOICE:  The RX4 can be tuned to any L-Band upklink (preferably
set to Wideband FM) for experiments.  Using Wideband FM on the uplink and
S-Band downlink solves the severe Doppler problem, though amateurs will
have to build their own WFM exciters.

(LB) L-BAND BENT-PIPE DIGITAL:  Using WFM digital modulation fed to the
the wideband FM S-band downlink, data rates up to 38.4 KHz or higher can
be accomodated in a bent-pipe mode.

(LD) L-BAND DIGITAL:  Unfortunately, The S-Band transmitter shares the
same data modulator as the UHF transmitters, so any use of S-Band for high
on-board-originated data rates precludes any other digital modes or data
rates on UHF at the same time.


The concept of a User Service Agreement worked well for PCsat.  After some
initial consternation, most users in the Amateur Satellite Service soon
realized that having a well known and published set of guidelines,
recommendatoins, and rules for standard operation were in their own best
interest.  Having operating parameters, protocols and clearly defined
operating objectives published and available in real time via a WEB page
and via the live downlink bulletins gave users clear guidance how to
optimize operating modes for everyone.

For example the WISP channel clearly only works well if all users are
using the WISP protocol which enforces unbiased sharing.  SImilarly, the
APRS channel works best if users adhere to the standard APRS duty-cycle
recommendations and power levels.

These same guidelines should also apply to the Voice transponder.  That
is, there will be times when free-for-all QSO's are invited, but in
general it has clearly been established that maximum effectiveness of a
voice transpodner usually occurs when there is a net control operator
operating as a directed net.    The details of recommended VOICE operating
nets via LEO birds is beyond the scope of this text, but is included on


AMSAT-NA president Robin Haughton and DIrector RIch Hambly have already
begun the groundwork for establishing the Echo Operations Committee.  I
look forward to the operations of this body and the potential for good
leadership and efficient operations planning for this new satellite.  The
first item should be the declaration of a mission statement which will
serve as the guiding principles for operations.  A possible strawman draft
might be:


THe mission of ECHO will be to serve the communications needs of users
worldwide in the Amateur Satellite Service in accordance with the rules
and objectives of the ITU and IARU.  Such usage will balance the needs for
reliable routine digital and voice communications as well as experimental
modes.  Included in this service is the recognition of the educational and
out-reach potential of this simple-to-use, but highly flexible spacecraft
as well as its potential use for mobile and portable operation in
wilderness regions and support of emergency or special event comunications

Respectuflly Submitted

Bob Bruninga, WB4APR

Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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