George Henry wrote:
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "George Henry" ka3hsw@earthlink.net; "amsat bb" amsat-bb@amsat.org Sent: Saturday, September 23, 2006 5:08 PM Subject: Re: [amsat-bb] Eagle and emergency traffic (was Re: Galileointerference on L band)
Why would it be available for only short periods? Eagle is a HEO.
73,
John KD6OZH
I said RELATIVELY short periods... what is the maximum time that the proposed data transponder will be available to a given ground station, with favorable squint angles, on any given orbit? What is the TOTAL, cumulative access time per day? From the perspective of an emergency manager or disaster team captain, it is certain to seem small when 24/7 service is available from other sources, particularly sources that they have already invested in. And since the design team is looking into their crystal ball at what the state of things will be 5 years down the road at launch, surely they have seen that the entire internet access landscape is sure to have undergone a sea change by then? (Bill Gates sure seems certain of that...)
I repeat: if the design team has anything from the NGOs to bolster the claim that they (NGOs) "need it for emergency data communications", then let's see it.
I don't believe anyone said we had a directive to provide a service. How could we have such a directive when we don't have the satellite designed yet? What NGO or government agency do you know would empower us to do something or even ask based on a hope we get our facility launched in the next half decade? I wouldn't go see them about using us in their planning until such time as the facility was actually available. That does not make it a sin or a fault to hope to provide that facility and to think about what it would take to make it possible. I certainly don't hang my head in shame because I have those thoughts. In fact, I am kind of proud of us for taking it into consideration.
Eagle is being designed to provide long term access per bird as compared to previous and planned P3 birds. The advanced communications package is being designed around the use of phased arrays. The phased array design is targeting 70% of the orbit to be usable per bird. If we choose to stay in a 12 hour orbit, that is 8-ish hours per orbit. The only way this can be made to work in a usable fashion, providing voice, conferencing, data/file transfer is the use of digital signaling. Admittedly, no ground station will see every orbit since we are also aiming for an equatorial orbit. We need more than one bird.
73's Bob N4HY