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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/6QJ6IZF75J3GVEODIJJDD7F5ZYVIZPCJ/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "[email protected]", "message_id_hash": "6QJ6IZF75J3GVEODIJJDD7F5ZYVIZPCJ", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/6QJ6IZF75J3GVEODIJJDD7F5ZYVIZPCJ/?format=api", "sender": { "address": "wb4gcs (a) amsat.org", "mailman_id": "87014499e012476c8198fad186f7f963", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/87014499e012476c8198fad186f7f963/emails/?format=api" }, "sender_name": "Jim Sanford", "subject": "[amsat-bb] [Fwd: S-band on Eagle]", "date": "2006-09-08T02:53:55Z", "parent": null, "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2JQIKIHS5G4TRELMVZCSX7IBSI2R4F3K/?format=api", "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/3NAK5ZS5SWLYIPKAYR64A75GZA3SWIAE/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "\n\n-------- Original Message --------\nSubject: \tS-band on Eagle\nDate: \tThu, 07 Sep 2006 21:40:37 -0400\nFrom: \tJim Sanford <[email protected]>\nTo: \[email protected]\n\n\n\nLadies and gentlemen:\n\nI have been reading the comments regarding the Eagle S-band downlink \ndecision. I herewith respond to some.\n\nAll along, the Eagle project has put a premium on hard science, rigorous \npeer review, and dispassionate analysis.\n\nAll along we knew there might or would be some changes to what we've \nbeen planning.\n\nWith several other issues on the move or decided, we took a few days in \nlate June to hammer out, based on science, the transponder situation. \nWe did multiple, independent link analyses, and all came to the same \nconclusion. We validated interference predictions with measurements \nthat have been taken. The conclusion is that S-band is marginally \nuseful as a downlink today (unusable in many locations), and by the time \nEagle is launched, and through it's lifetime, will be unusable. \n\nPersonally, I do not like this decision. I have S-band equipment that I \nwas looking forward to using. \n\nPersonally, I can live with this decision, and defend it to myself, let \nalone anyone else, because I am convinced that it is technically sound. \n\nAs one of you commented this evening, AO-40 wasn't exactly a rock \ncrusher on S-band. It worked, and adequately, at least on CW, but was \nnot great. As I reflect on my personal AO-40 experiences, I now \nunderstand that there are 2 reasons for my disappointment. Local noise \nwas one, and transponder distortion was another -- the latter will be \ncorrected by SDX. S-band on AO-40, by necessity not choice, got many of \nus out of our comfort zones and convinced us that microwaves really \naren't that hard. Let's enter the realm of S up and C down with that \nsame realization. \n\nREMEMBER THAT AMSAT IS DEVELOPING THE GROUND STATION ALONG WITH THE \nSPACE SEGMENT. \n\nYou will not be left on your own to develop ground equipment. You will \nnot be asked to mortgage your house; affordability by the masses is a \nkey component of the design for the entire system.\n\nComparison with AO-51 is an \"apples and oranges\" thing. The path losses \nare much different. FM is very unlike CW/SSB or wideband digital \nmodes. Remember that a goal of the Eagle system is that everything is \non all the time. No more matrix switches, no more schedules. We need \nup and downlinks to be useful throughout the entire orbit.\n\nWhy did we \"regress\" to U/V? For one reason, many of you asked for it, \nand some of us worked hard to somehow incorporate that capability in \nresponse to member's desires. The foot in the door was the utility of a \nV-band beacon in case everything else goes sour. The forcing function \nwas as follows. A goal of Eagle has always been some kind of hand-held \nor jump bag portable ground station capability for entry into the \nemergency area while the tsunami waters are receeding and the hurricane \nwinds are down to gale force. Many of us thought we could take \nadvantage of the gain in small antennas to do this on the microwaves. \nRigorous link analysis led us to the conclusion that the best place to \ndo this is U/V -- both from a RF/DC power perspective, and from a link \nstandpoint. This leads to the digital and \"traditiona\"l transponder \npackage for U/V, implemented in SDX.\n\nWhy not also include a (switchable) S-band downlink in parallel with the \nV-band? Remember, no switches. Also, we run into an antenna space \nproblem. We've already increased the size of the spacecraft from where \nwe started, and for many reasons, do NOT want to build something as \nlarge as AO-40.\n\nA couple of you have commented this evening that perusing EaglePedia has \nnot revealed the details of the decisions. That is because, while Bob \nMcGwier (N4HY) and I have been working on the report of the meeting, it \nis not public. We've been working hard on it since June, in and around \nother AMSAT, ham radio, and life events. Shortly after I push send on \nthis message, I'll begin my final look at that document prior to public \nrelease. \n\nBefore I go spend time with the spousal unit TONIGHT, I will finish it \nand publish it. I will send an announcement on the amsat-bb that it is \npublic. To read the report, go to the EaglePedia main page, and select \nproject index. From there, select Team and Meetings, and there will be \nseveral options, not all public. The San Diego meeting minutes will be \nobvious and public.\n\nSeveral of you have commented, \"If S-band is unusable, why is it flying \non P3E?\" Fair question, but I can't answer for AMSAT-DL. I DO know \nthat the P3E system design is considerably older and farther along than \nEagle. Eagle design decisions were made based on the best information \nin June of 2006.\n\nAspects of this discussion have been worthy of /dev/null. More aspects \nof this discussion have raised valid points and reasonable questions, \ndeserving of response, which is why I've been composing this note for \nthe last four hours or so.\n\nA few have raised the old allegation of the builders doing what they \nwant, without regard to users needs. This is not true. While the \ndesire to advance the state of the art (part of amateur radio's \njustification for existence and allocation of valuable spectrum) leads \nto enthusiasm and study of potentially useful new techniques, this \ndesire had no impact on our analysis-based decisions. We started with \nrequirements and services, and explored what would deliver. \n\nI thank all of you for your interest and support. Your Eagle team is \nworking hard to develop a system that will serve our needs, as well as \nadvance the state of the art. As promised, we are making decisions \nbased on sound, peer-reviewed science, not anybody's opinions or desires.\n\nPlease read the report, study the spreadsheets, download the excel file \nand play with it. If you can, make your own measurements and put those \nnumbers into the spreadsheet. I think you'll understand how these \ndecisions were reached.\n\nAfter contemplating the report, send me your questions. I'll either \nrespond or forward to he who can best respond. Another fundamental \ntenet of the Eagle project is openness, so you have a right to a \nresponse to a rational question. Please recognize that we're volunteers \ntoo, and subject to the realities of day jobs, families, and a real \nlife. Response may not be instantaneous.\n\nThanks again and very 73,\n\nJim\n\nJames A. Sanford, PE\nEagle Project Manager\[email protected]\n\n\n\n", "attachments": [] }