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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/L7GAR5KQOIWF5M5HM6AR7IGBYQZGWQFR/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "[email protected]", "message_id_hash": "L7GAR5KQOIWF5M5HM6AR7IGBYQZGWQFR", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/DNIFMRNNSZ7S7QW6RV73AQ77G4NWPEMO/", "sender": { "address": "rwmcgwier (a) comcast.net", "mailman_id": null, "emails": null }, "sender_name": "Robert McGwier", "subject": "[eagle] Re: Module Temperatures", "date": "2006-10-14T16:07:12Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/D7DWUURKWBDSFPR3Z65M2NLJOWM2NY5S/", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "I think we should plan on sharing the antennas and we need to think \nabout the omni's for -Z eventually. These are a lower priority than \nother tasks at the moment but they should be figured into the \"block \ndiagram\" in our minds.\n\n\nBob\n\n\n\nJim Sanford wrote:\n>\n> Will we share antennas or add some?\n> Jim\n>\n>\n> Robert McGwier wrote:\n>> I believe we should use Mirek's command receiver on L band as adapted \n>> for our purposes. If we want a redundant one for any reason, we do \n>> that one on 70cm. The command receiver should feed the IHU-3 SDR for \n>> any normal commanding and any reset vector decoder we choose to enable.\n>>\n>> The issue is straightforward. Any module that needs a heat sink will \n>> have been designed to be kept cool when the spacecraft is receiving a \n>> large thermal input from the sun. When this thermal input is removed, \n>> the same radiation cooling that was keeping the module cool will \n>> continue to operate irrespective of the solar input. That module will \n>> get cold over time. If the bottom temperature stops the unit from \n>> operating properly and it is a command receiver, this is not a good \n>> thing. I believe we should have dedicated command receivers anyway and \n>> these to do not need 80 dB of dynamic range and can be made narrow \n>> band. Our solar eclipse pattern has been given a preliminary analysis \n>> for the proposed orbit and we will be subjected to eclipses of \n>> insufficient duration to cause us severe thermal problems but what \n>> thermal issues there are need to be understood and this is what Dick is \n>> warning us about. This analysis of the eclipse pattern was also the \n>> basis of my analysis that it would take well over a decade to subject \n>> any Li-ion battery to sufficient cycles to worry about.\n>>\n>> Bob\n>> N4HY\n>>\n>>\n>> John B. Stephensen wrote:\n>> \n>>> The SAW filters work down to -35 C and the ICs to -40 C so its not too \n>>> far off. It's easy to use a lower power RF amplifier and mixer which \n>>> will lower the input intercept. Right now, the receiver is designed to \n>>> tolerate direct hits from PAVE PAWS at any two frequencies outside the \n>>> IF passband. As the input intecept is lowered, the percentage of \n>>> pulses that cause interference increases, but the receiver won't go \n>>> completely deaf as was reported on earlier satelites.\n>>> \n>>> 73,\n>>> \n>>> John\n>>> KD6OZH\n>>>\n>>> ----- Original Message -----\n>>> *From:* Dick Jansson-rr <mailto:[email protected]>\n>>> *To:* AMSAT Eagle <mailto:[email protected]>\n>>> *Sent:* Wednesday, October 11, 2006 17:51 UTC\n>>> *Subject:* [eagle] Module Temperatures\n>>>\n>>> Last evening I tried to convey the concept that the\n>>> critical-command modules needed to be of low-power design to\n>>> insure their operability during the occasional rather lengthy\n>>> eclipse cooling of the spacecraft. My message apparently did not\n>>> sink in. John reports that his design of such a U band receiver\n>>> would be dissipating some 3.5W due to its bullet-proof nature\n>>> against 3rd-order IM products needed for protection on the U band.\n>>> \n>>> If we go forward with such a module of that nature, it will need\n>>> to have thermal control tapes on it to provide a mean emittance of\n>>> about e=0.45. In a 3 hour eclipse we can expect to see spaceframe\n>>> temperatures down to -100°C (173K) or lower. With such an\n>>> environment John's module would be expected to see temperatures\n>>> down to at least -44°C, which is a bit frosty for electronics that\n>>> are expected to provide the critical services of commanding the\n>>> spacecraft. Such operating temperatures are not felt to be\n>>> advisable for that service.\n>>> \n>>> If John's module were of the 1W category, temperatures of the\n>>> receiver could be expected to be in the range of -15°C to -20°C\n>>> which would be more operable for the service.\n>>> \n>>> The above numbers are, of course, based on estimates which will be\n>>> confirmed after we have the new spaceframe fully designed and\n>>> analyzed. The \"warmer\" temperatures of the lower power modules are\n>>> those that have been experienced and measured by telemetry from\n>>> AO-10 and AO-13. These projections are thus based on 25 years of\n>>> experience in these design concepts.\n>>> \n>>> /Dick Jansson/\n>>> _---------------------------_\n>>> [email protected] <mailto:[email protected]>\n>>> _---------------------------_\n>>>\n>>> \n>>>\n>>> ------------------------------------------------------------------------\n>>> _______________________________________________\n>>> Via the Eagle mailing list courtesy of AMSAT-NA\n>>> [email protected]\n>>> http://amsat.org/mailman/listinfo/eagle\n>>>\n>>> ------------------------------------------------------------------------\n>>>\n>>> _______________________________________________\n>>> Via the Eagle mailing list courtesy of AMSAT-NA\n>>> [email protected]\n>>> http://amsat.org/mailman/listinfo/eagle\n>>> \n>>> \n>>\n>>\n>> \n\n\n-- \nAMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,\nTAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair\n\"You see, wire telegraph is a kind of a very, very long cat.\nYou pull his tail in New York and his head is meowing in Los\nAngeles. Do you understand this? And radio operates exactly\nthe same way: you send signals here, they receive them there.\nThe only difference is that there is no cat.\" - Einstein\n\n", "attachments": [] }