Eagle Project Manager Jim Sanford, WB4GCS |
Matt Ettus, N2MJI, makes a point during his AMSAT Space Symposium presentation. |
The AMSAT-NA Space Symposium and Annual Meeting took place in San Francisco October 6-8. |
Ham radio satellite guru Tom Clark, K3IO |
Howard Long, G6LVB, demonstrates a prototype SDX. |
AMSAT-NA President Rick Hambly, W2GPS, addresses the AMSAT-NA annual meeting. The 2007 AMSAT Symposium and Annual Meeting will take place in Pittsburgh, he announced. |
SAN FRANCISCO, CA, Oct 9, 2006 -- AMSAT-NA has announced it's revamping the design of its Project Eagle satellite, currently in the development stages. The next-generation, high-Earth orbit (HEO) satellite now will take maximum advantage of software-defined transponder (SDX) technology to offer a broader range of easily accessible Amateur Radio payloads. The AMSAT Board of Directors okayed the Eagle upgrade plans during the 2006 AMSAT-NA Space Symposium and Annual Meeting held here October 6-8. Eagle Project Manager Jim Sanford, WB4GCS, outlined the changes at his Space Symposium forum October 7.
"The structure which we have been presenting for several years is not going to meet our mission needs," Sanford explained. "We have moved on to a later structure."
AMSAT's plans call for an mode U/V transponder for SSB, CW and other modes. The design goal is that it be usable over 75 percent of Eagle's orbit by an AO-13 or AO-40-capable ground station. A second mode L/S1 (1.2/2.4 GHz) transponder for SSB, CW and other modes using fixed antennas also should be accessible by an AO-13 or AO-40-capable ground station.
Texting via Ham Radio Satellite
Something new to Amateur Radio satellites is a planned low-rate text messaging system similar to cellular telephone SMS. Sanford said the text-messaging capability may prove valuable for providing emergency and disaster communication. It will operate in mode U/V and also will be available to modest ground stations over 75 percent of Eagle's orbit.
Advanced Communications Payload
Eagle will also carry an advanced communications payload (ACP). Using advanced signal processing and RF techniques, the ACP will accommodate voice communication using an S2 band (3.4 GHz) uplink and a C band (5.8 GHz) downlink via a single 60 cm dish on the ground. As an alternative -- for stations in those parts of the world where 3.4 GHz is unavailable -- Eagle will provide an additional L band uplink that will require a separate uplink antenna at the ground station.
The ACP also will offer high data rate communication including the possibility of full-motion compressed video in S2/C mode at modest power levels. AMSAT predicts ground stations should be able to access this mode using a 2 meter dish. The same mode also could support an Internet link. Ground-station antennas for Eagle may even pass muster in neighborhoods governed by private deed covenants, conditions and restrictions (CC&Rs), Sanford suggested.
AMSAT says it will develop and make available an affordable ground segment for the ACP. Sanford said AMSAT is conscious of the need for affordability. "We're working hard to meet the needs of the working ham," he said.
New Satellite User Base
During his presentation on the ACP, Matt Ettus, N2MJI, said one of the goals of the package is to open up the satellite to a new base of users, not just restrict it to elite satellite operators and sophisticated ground stations. Embracing SDR technology simplifies signal handling, he explained, because going digital is just a matter of transmitting bits up and down.
"The satellite doesn't really care what the bits mean," he said. The satellite "just reflects bits," and most policy-type issues will be handled by ground stations. "One of the most common uses will be digital voice."
The satellite's signal will present one wideband downlink containing multiplexed data. As Ettus explained, bandwidth is cheap in comparison to power, and digital technology allows for non-linear amplifiers, making things even less complex. "There will be room for many, many carriers in the passband," he predicted. The mix of users would be apportioned among both low and high-rate modes, depending on overall traffic.
Electronic Antenna Pointing
Plans call for electronically steering the satellite's antennas to mitigate the effects of the spacecraft's spin and maximize the spacecraft's accessibility. In a subsequent forum, AMSAT board member and well-known satellite expert Tom Clark, K3IO (ex-W3IWI), discussed some of the mathematics and physics that would permit steering a 37-element S band antenna array on Eagle.
"We would intentionally steer that pattern, so the array is always pointing toward Earth," Clark said, regardless of spin factor. He described a system of interferometers to do the pointing on the basis of "master beacon signals" uplinked from different points on Earth's surface. "It [Eagle] will measure where they are and know where to point the beam," he explained.
SDX Prototype Demonstrated
In a presentation on applying SDR techniques to satellite transponders, Howard Long, G6LVB, described and demonstrated a prototype SDX board. "This is the holy grail of what we've been trying to do," he told his audience.
Long showed how his hand-soldered SDX could be configured to accommodate various signal strengths and types within the same passband and even to easily notch interfering signals quickly and flawlessly. He also urged his listeners not to shy away from DSP experimentation; two years ago, he pointed out, he had no digital signal processing (DSP) experience whatsoever and conceded that his math skills were a bit rusty. "I hope I can be an inspiration," he said.
Serious Money
Sanford concluded his presentation by saying it's time to take the AMSAT board's concrete decisions and plan, schedule and build Eagle. "We're about to start spending some serous money," he said. During a later question-and-answer session, Sanford stressed that reliability of the ultimate Eagle satellite is a key goal. "I want no single-failure mission kills on this satellite," he said.
Clark said Project Eagle still needs to raise $33,500 by December, "and we're going to need more in the years coming." Eagle could launch by 2010. The whole project will cost some $600,000.
Excitement for the Sat
During the AMSAT-NA annual meeting October 8, President Rick Hambly, W2GPS, expressed his enthusiasm for Project Eagle. "I'm so excited about this project," he said. "I think it will be the greatest thing we've ever done!"
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