[amsat-bb] Re: ideas
bruninga at usna.edu
Thu Jan 11 07:16:31 PST 2007
> The cubesat team at the University of Louisiana is in the
> process of defining its second mission for its cubsat
> project. The team has decided to fly a cubesat that has a
> educational component. We are asking for ideas that would
> excite K through 12 students that can be flown on a cube sat
> i.e. 1 watt of dc power in a 4 inch cube.
DIGIPEATING MISSION: Please consider an AX.25 packet digipeater
on 145.825 to continue to add to the educational amateur
satellite constellation there. With multiple satellites on one
frequency providing a generic bent-pipe digipeater like
PCSAT,ANDE and RAFT, studnets would have dozens of passes per
day to chose from for school experiments instead of just a few.
Remember PCSAT is only alive 3 weeks out of the year, and ANDE
and RAFT are all so low as to burn up in a year or less, and the
digipeater on ISS is inoperative.
So we need a pipeline of university satellites targeting this
continuing 145.825 digipeating mission so that new satelites
replace or add to old ones. If we can get up to 6 satellites
doing the same thing on that same frequency, then we could
guarantee students worldwide access to at least one of them
during any CLASS hour anywhere at any time.
INTERNET LINKED GROUND STATION NETWORK: In addition, we have a
worldwide system of ground stations capturing the downlink on
145.825 and feeding it live to the internet so that any one
school's satellite can be seen at any time over any country
live. This also makes it much better in academia, so that
classes are not limited to access to their satellites only a few
times a day but over any other ham radio country as well.
NO SPECIAL HARDWARE: In addition to using 1200 baud AX.25 which
almost every ham radio operator has access to, ground stations
these days do no even need any special hardware or TNC.
Soundcard packet implementations can be used so that schools
only need a laptop and a radio to participate.
USER MISSIONS: Making the sateellite be a digipeater does not
restrict the applications. Any digital application can be used
simply by the application on the gorund. The satellite is only
a bent pipe relay. SCHOOL-to-SCHOOL communications, BBS
messaging, APRS position and status tracking of mobiles, boats
Hikers, etc... ALL downlinks available real time on the
internet (see http://pcsat.aprs.org ) Any future student
applications can use this bent pipe transponder. Consider the
Naval Academy's plan to deploy ocean going environmental sensor
buoys to digipeat their data back to the school from anywhere in
the world on this channel (see
STUDENT PROJECTS: An advantage of this type project to other
schools is that those schools that cannot affort to build a
satellite, can isntead have students building applications to
USE the existing 145.825 relay system and internet data
AUX PAYLOADS: In addition, the pcaket up and downlink can be
used for serial data to any additional spacecraft experiment.
PCSAT-1 had a GPS on its serial port. ANDE and RAFT have
text-to-speech synthesizers (40 mA) that can speak special
packets sent to them. A Naval Academy favorite packet
transmitted by my students is "Go Navy, Beat Army" ... Etc The
advantage of the packet-to-voice synthesizer is that all
students can hear it, not just those with packet.
KISS PRINCIPLE. And the neat thing is that to do all of the
above the satllite only needs a RX, TX and a TNC. No special
software or CPU on board since modern TNC's have all of the
above built in. Telemetry, beacons, command/control, remote
password protected logon by the command station, digipeating,
serial port access, 8 bit parallel I/O, serial port, etc. The
only problem is that a standard off-the-shelf TNC such as the
KPC-3+ is hard to fit in a 4" cube. Though it could be
LASTLY, operating up and down on 145.825 has a 9 dB advantage in
the link budget BOTH ways to stations with simple OMNI antennas
compared to using UHF. A 2 watt transmitter can easily be heard
on an HT. And since the TX is only on for brief TX packet
bursts only over the 10% of the world that is amateur radio
populated, and since even over the USA, the peak load on the
transmitter cannot exceed about 30 or 40% due to simplex
digipeating, the overall TX load on the small satellite is only
3% of nominal TX power, so even a 2W TX could be used and only
require an average orbit power of .12W, easy for a cubesat. You
can further reduce that by limiting most modes to daylight
(school) hours only and not wasting power in the dark.
MOBILE SATELILTE OPERATIONS: And lastly, these satellites
provide the first viable mobile AMSAT communicaitons capability
since they can be heaerd by a mobile whip antenna. In today's
times, many hams can only find time to oeprate ham radio while
mobile. We should b e designing a constellation of satellites
on 145.825 to give them the coms pipeline they need.
All of our PCSAT,ANDE and RAFT designs based on the above can be
found via our web pages. Simply GOOGLE for ANDE OPS and you
should find it. It has links to all the satellites.
US Naval Academy Satellite Lab
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