題圖：MH370的搜求牽動(dòng)全世界
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06:36 6/19/2014
如CNN截圖所示：新建議的搜救區(qū)域位于南緯36.02, 東經(jīng) 88.57 。
"While there remain a number of uncertainties and some disagreements as to the interpretation of aspects of the data, our best estimates of a location of the aircraft (is) near 36.02 South 88.57 East," according to the statement, which was approved by 10 named experts.
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21:06 6/18/2014
五個(gè)獨(dú)立的的計(jì)算機(jī)模型一致定位了新的飛機(jī)失事判斷點(diǎn)，仍然位于印度洋，但是距原先的搜尋區(qū)域有數(shù)百英里。
CNN：Outside group tells governments where to search for Flight 370
A group of independent experts -- who prodded authorities to release satellite data on Malaysia Airlines Flight 370 -- says it thinks it knows the approximate location of the missing aircraft.
Five separate computer models all place the plane in a tight cluster of spots in the south Indian Ocean — hundreds of miles southwest of the previous search site.
所有的報(bào)道都來(lái)源于周二BBC的地平線節(jié)目
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20:01 5/27/2014
Inmarsat公布了衛(wèi)星數(shù)據(jù)——————————————————————————————————————————
21:02 5/27/2014
數(shù)據(jù)說(shuō)明部分解讀（斜體是原數(shù)據(jù)的說(shuō)明 正體是我的解讀）
Inmarsat的衛(wèi)星定時(shí)與MH370飛機(jī)上的發(fā)動(dòng)機(jī)監(jiān)控模塊通信，通信過(guò)程無(wú)人為擾動(dòng)的可能性，因此是判斷飛機(jī)未知的重要信息。
Inmarsat提供了了兩種測(cè)量數(shù)據(jù)BTO和BFO，分別是通信信號(hào)的時(shí)間偏移和頻率偏移，前者可以推算衛(wèi)星與飛機(jī)之間的距離，后者可以根據(jù)多普勒效應(yīng)推算飛機(jī)的速度（具體對(duì)利用多普勒效應(yīng)推算MH370未知的原理見(jiàn)Ping Rings from the Inmarsat-3F1 Data），結(jié)合兩者完成對(duì)飛機(jī)位置的判斷。
Understanding the Burst Timing Offset (BTO) values:
這一部分是講數(shù)據(jù)中BTO 突發(fā)時(shí)間偏移的含義
The round trip time for a message is a combination of:
round trip time for a message 是指一條衛(wèi)星報(bào)文傳遞的時(shí)間 包含傳播時(shí)延和處理時(shí)延
Time from the ground station → satellite → aircraft → satellite → ground station
這一部分講的是衛(wèi)星報(bào)文的傳遞路徑 從地面站->衛(wèi)星->飛機(jī)->衛(wèi)星->地面站
這個(gè)路徑的長(zhǎng)短影響著傳播時(shí)延因?yàn)?br> 傳播時(shí)延 = 傳播路徑長(zhǎng)度/光速
根據(jù)傳播時(shí)延推算路徑長(zhǎng)度是確定飛機(jī)位置的重要參數(shù)，術(shù)語(yǔ)是測(cè)距定位，GPS主要就是靠測(cè)距定位。Processing time within the ground station, satellite and aircraft terminal, which are constant
報(bào)文在傳遞過(guò)程中，不僅傳播路徑消耗時(shí)間 ，衛(wèi)星、地面站、飛機(jī)上的無(wú)線電臺(tái)收發(fā)、處理報(bào)文需要的時(shí)間也影響總的時(shí)延，稱之為處理時(shí)延（Processing time）。Inmarsat的報(bào)告認(rèn)為不同報(bào)文的處理時(shí)延是固定的，考慮到衛(wèi)星傳輸?shù)奶匦?，這一看法是合理的。
因此，
總時(shí)延（BTO） = 傳播時(shí)延+處理時(shí)延
我們關(guān)注的是傳播時(shí)延，要消除處理時(shí)延的影響，處理時(shí)延固定且未知（我這里假設(shè)未知，也許inmarsat 通過(guò)平時(shí)的實(shí)驗(yàn)和數(shù)據(jù)積累掌握了處理時(shí)延），一般可以通過(guò)多次數(shù)據(jù)差分的方法消除，這樣得到的距離也應(yīng)該是距離差。
The BTO is a value (in microseconds) relative to a terminal at a nominal fixed location. Only R-Channel messages are used.
這段話是說(shuō)這個(gè)通信中只用了一個(gè)位置固定的地面站。
The BTO therefore allows the determination of the distance between the satellite and the aircraft. It does not provide the actual aircraft location
這里講由于只有一顆衛(wèi)星參與通信，每一有效的測(cè)量時(shí)刻時(shí)刻也只能得到一個(gè)傳播實(shí)驗(yàn)，因此無(wú)法準(zhǔn)確定位（GPS需要四顆以上的衛(wèi)星才能準(zhǔn)確定位）。
因此，利用BTO得到的信息無(wú)法完全用于飛機(jī)的定位，需要其他信息輔助。
Understanding the Burst Frequency Offset (BFO) values:
Burst Frequency Offset (BFO)是指由于飛機(jī)高速運(yùn)動(dòng)產(chǎn)生的信號(hào)的頻率偏差。需要注意的是，參與MH370衛(wèi)星通信的海事衛(wèi)星部署于地球靜止軌道（GEO），相對(duì)于地球靜止，本身并不引入多普勒頻率偏移。（后面還有具體解釋）
The transmission signal path from the aircraft has two components affected by Doppler shift; between the satellite and aircraft, and between the satellite and ground station.
這里說(shuō)有兩個(gè)因素會(huì)引入多普勒頻移，衛(wèi)星相對(duì)地面站的運(yùn)動(dòng)，和飛機(jī)相對(duì)衛(wèi)星的運(yùn)動(dòng)。
The following need to be considered when computing the expected frequency offset:
o Inmarsat Classic Aero mobile terminals are designed to correct for aircraft Doppler effects on their transmit signals. The terminal type used on MH370 assumes a stationary satellite at a fixed orbital position
這里將Inmarsat 為MH370提供的衛(wèi)星通信終端具有修正多普勒頻移的功能，也就是說(shuō)衛(wèi)星到達(dá)飛機(jī)的信號(hào)的多普勒頻域會(huì)被消除，同時(shí)飛機(jī)認(rèn)為衛(wèi)星靜止，因此飛機(jī)返回給衛(wèi)星的電波中包含與飛機(jī)速度相關(guān)的多普勒頻率偏差。
o An individual aircraft terminal will have a fixed frequency bias
這里說(shuō)明飛機(jī)上的衛(wèi)星終端由于晶振的不確定性等因素會(huì)引入一個(gè)頻率偏差，但是該偏差是固定的。
也就是說(shuō)，飛機(jī)到達(dá)衛(wèi)星的信號(hào)的頻率為f2，而理想的頻率為f1時(shí)，f2受到多普勒頻移fd和晶振偏差fo的影響，即
$$
f_{2} = f_{1} + f_u0z1t8os+f_{o}
$$
我們關(guān)注的是fd，即多普勒頻移， 由fd可以推算飛機(jī)的速度。
o Satellite, terminal and ground station oscillator stability
這里說(shuō)明地面站、終端、和衛(wèi)星的晶振是穩(wěn)定的，即只會(huì)引入固定的頻率偏差，提示我們可以用差分的方法來(lái)研究不同時(shí)刻多普勒頻移的變化。
o The correction applied by the Automatic Frequency Control (AFC) system in the ground station partially compensates for the satellite to ground station Doppler
