概述

1.1

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盡管如此，地面、海上航船和空中飛行器仍可繼續接收121.5兆赫頻率，這一頻率仍是用于定位遇險人員最有效可靠的系統。因此，求救無線電信標應為雙頻系統，方可確保精準定位。

系統構成

示位標

遇險示位標實際上就是一臺可以完全獨立工作的全自動發信機，示位標有三種形式：航空用緊急示位發射機（ELT），航海用緊急無線電示位標（EPIRB），個人位置示位標（PLB）。遇險示位標使用的頻率有：121.5MHz、243MHz、406MHz。當用戶遇險后，遇險示位信標可以通過人工或者自動由遇險時的撞擊、水浸而激活（信標激活后可以存活48/小時），發出121.5/406MHz的遇險報警信號，經衛星轉發后，由遍布全球的本地用戶終端（LUT）接收并計算出遇險目標的位置，隨后經國際通信網絡通知遇險地區的相關搜救部門進行搜救。

衛星星座

搜救衛星星座是由前蘇聯的COSPAS衛星和美國的SARSAT衛星組成，衛星高度為：850～1000km，衛星運行軌道為極軌道，現有六顆衛星在工作。搜救衛星的主要任務是對遇險示位信標發出的遇險報警信號進行變頻、存儲、轉發等處理，然后送給本地用戶終端（LUT）；對121.5/243MHz的遇險報警信號以下行頻率1544.5MHz實時轉發給本地用戶終端（LUT）進行處理；而對406MHz的遇險報警信號既可以以下行頻率1544.5MHz實時轉發給本地用戶終端（LUT）進行處理，也可以先存儲起來遇到LUT再轉發。由于該系統的衛星軌道較低（850～1000km），單顆衛星覆蓋地球的面積比地球同步靜止衛星小。因而，在目前六顆衛星工作的情況下，對遇險目標來說存在著一定的等待時間，尤其是在靠近赤道地區，兩顆衛星飛越同一地區的時間間隔最長可達1.5小時。因此，一些國家現在正在考慮使用地球同步靜止衛星實現對信標信號的實時轉發，以消除衛星的等待時延。目前，由印度發射的INSAT－2B同步衛星裝備有406MHz轉發器，可以實現對中國全部陸地和海域的實時覆蓋。

地面分系統

地面分系統包括本地用戶接收終端（LUT）和搜救任務控制中心（MCC）兩大部分：（1）本地用戶接收終端（LUT）,本地用戶接收終端的作用是：跟蹤搜救衛星并接收衛星轉發下來的遇險示位信標信號和數據，然后解碼、計算并給出信標識別碼和位置數據，同時又實時修正衛星的軌道參數，把信標的報警數據和統計信息送給相應的搜救任務控制中心（MCC）。（2）搜救任務控制中心（MCC）,搜救任務控制中心（MCC）必須和本地用戶接收終端（LUT）相聯接，一個MCC至少要聯接一個LUT，美國的MCC聯接了12個LUT，其中有一個是靜止軌道的LUT。MCC的主要功能是：收集、整理、儲存和分類從LUT與其它MCC送來的數據；在COSPAS/SARSAT系統內與其它MCC進行信息交換；過濾虛假報警，解除模糊值；把報警和定位數據分發到有關的搜救協調中心（RCC）或搜救協調點（SPOC）。目前世界上已經有21個國家建立了38個LUT，共有19個MCC處于工作狀態。LUT的地理分布可以把地球的大部分表面覆蓋，有些地區特別是東南亞地區由多個LUT重疊覆蓋；個別地區如非洲南部尚未建有LUT，但該系統可以由搜救衛星利用星上存儲器把遇險信號存儲起來攜帶信號飛行，直到有LUT接收到此遇險信號。

How it all works together

   Search and Rescue (SAR) instruments are flown on board Low Earth Polar Orbiting (LEO), Medium Earth Orbiting (MEO) and Geostationary Earth Orbiting (GEO) satellites provided by the United States, Russian Federation, India, and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). These satellites can detect signals coming from the Earth’s surface transmitted by 406 emergency distress beacons. These beacons operate on a 406MHz frequency and are battery powered radio transmitters designed solely to send a distress signal if activated. Once a beacon is activated it begins to transmit a continuous radio signal which is first picked up by the satellite instrumentation, then used by search and rescue to locate the emergency and render assistance.

   There are three types of 406MHz beacons, each with unique properties depending on the type of environment it is designed for: Emergency Locator Transmitters (ELTs) used by the aviation community, Emergency Position Indicating Radio Beacons (EPIRBs) used in the maritime environment, and Personal Locator Beacons (PLBs) used by individuals in multiple wilderness activities.

   When activated, ELTs, EPIRBs, and PLBs transmit the distress signal on the 406 MHz frequency. This signal frequency has been designated internationally for use only for distress. Imbedded in this frequency is a unique digital code called a HEX ID. The HEX ID identifies the type of beacon and, if the beacon is registered, important information that helps search and rescue (SAR) specialists determine the best course of action.

   This information can include: who the beacon owner is, the type of aircraft or vessel the beacon is associated with (for ELTs and EPIRBs), emergency points of contact, flight plans, float plans and wilderness trip plans, and much more. After the satellite receives a beacon signal, it relays the signal to ground stations referred to as local user terminals (LUTs). The LUT processes the data, computes the location of the distress beacon, and transmits a decoded alert message to its associated national Mission Control Center (MCC). This happens almost instantaneously after the initial beacon signal is received.

    The MCC then automatically performs matching and merging of alert messages with other received messages, geographically sorts the data, and transmits a distress message to the closest appropriate SAR authority such as a national Rescue Coordination Center (RCC), a foreign SAR Point of Contact (SPOC) and another MCC if the beacon is for example registered to another country. The RCC investigates the beacon alert and launches rescue assets to find the parties in distress if the distress is deemed authentic. This can happen much quicker when the beacon is properly registered.

   Return Link Service (RLS) is a new Cospas-Sarsat system enhancement which is coordinated by the French Space agency, CNES (Centre national d’études spatiales). This is an option built into the next generation 406 beacon itself.

In the case of the United States, the U.S. Mission Control Center (USMCC) receives distress signal data from its LUTs as well as other MCCs that have picked up the signal. It then transmits the distress message information to the closest U.S. national SAR services, such as the U.S. Air Force or U.S. Coast Guard RCCs, depending on the type of distress and its location.

   The USMCC also transmits distress messages internationally to SPOCs located in other countries that might have assets in closer proximity to the distress, even though the distress situation is technically taking place within the USMCC service area.

 

搜救系統介紹

自我國加入國際搜救衛星組織以后，交通運輸部始終關注著全球衛星搜救系統的技術發展。1991年，北京全球衛星捷救系統為我國建設的“全球海上遇險與安全系統工程”的一個子系統，開始了項目建設工作。并于1998年1月26日順利通過了國際組織的入網測試，進入全功能運行狀態。同時，我國在國際搜救衛星組織的身份變更為“地面設備提供國”。全部設備現安裝在北京交通部辦公大樓內。北京系統建成后，在我國的版圖上實際已建有三套全球衛星搜救系統。（1）北京系統的服務區覆蓋了除臺灣以外的我國所有陸地疆土和絕大部分的海域。（2）香港在北京之前就建有系統，目前由香港特別行政區海事處負責運行和管理，其服務區含蓋了北京系統無法實時覆蓋的我國南部海域和島嶼。（3）臺灣的系統建設幾乎與北京同步，目前由臺灣民航部門管理，其在國際組織的名稱是國際電信開發公司。其服務區覆蓋了全部臺灣島和環島的周邊海域。北京系統設備選用了當時國際上先進的、高性能HP-9000系列服務器和工作站。LUT采用了冗余備份結構，可以同時對兩顆衛星分別進行跟蹤，并由數據信號處理器對衛星下行信號中的121.5、243和406MHz信號進行實時處理；同時還可以對406MHz信號進行延時處理。MCC采用主/備雙機結構運行，目前通過X.25分組交換、AFTN航空專用通信網、Telex電傳和FAX傳真四種接口，與國際通信網聯接。按照國際組織編制的數據分布計劃，各MCC之間實時交換定位數據和衛星軌道參數等信息。四種通信接口依據可靠程度設有優先等級，互為備份，確保系統通信暢通。當北京MCC從自己的LUT或其他MCC收到報警數據后，首先判定示位標報警的位置是否在自己的服務區內。如果在服務區內，那么則立刻將報警位置和遇險示位標的登記信息，通知國家海事局；若報警位置在服務區以外，則通過西北太平洋區的節點MCC（日本MCC），將數據傳送給相關的國家。

搜救系統應用

在北京系統投入運行之前，我國的搜救指揮協調部門，主要是接收來自香港和日本系統傳來的報警信息。北京系統投入運行之后，幾年來，這套系統成功的擔負起了其搜救服務區內的遇險報警任務。截止到目前為止，系統已準確捕捉到二十八次真空的遇險報警，經國家海事局組織實施救助，使近四百余名遇險人員安全脫險。幾年來的實踐證明，北京衛星搜救系統的投入使用，極大地提高了我國海上和陸地的遇險報警能力，為我國遇險搜救手段的現代化，奠定了可靠的基礎。個人信標業務長期以來，遇險示位標基本都是作為船舶和飛機的必備設備，安裝在這些載體上的。其他還有極少數的示位標，是作為系統本身運行和技術發展需要，而設置的軌道修正和測試信標。全球衛星搜救系統，除了航空和航海兩大系統的用戶之外，隨著人們經濟活動的增加，對人命安全問題的進一步重視，加之國際組織成員國中要求提高系統利用率的呼聲強烈，在系統中已開發出便于攜帶、使用方便、針對個人使用的遇險示位標。體積只有現在流行的手機大小的個人用示位標，去年已經上市。美國、加拿大、丹麥、德國、挪威和俄羅斯等國，都先后開展了個人信標業務。從目前了解到的情況來看，國外個人信標的用戶，以政府的關鍵部門、軍事機構、高科技領域、國家重要的經濟部門、體育探險和大公司的高層人士為主。用戶只需在系統運行管理部門授權的公司，購買或短期租用遇險示位標，并交納一定的示位標購置費和年度注冊登記費或租金即可攜帶使用。國際市場上現有的遇險示位標的種類，完全可以滿足各種運輸設備和個人的需求。而在我國目前只有在遠洋運輸、漁業生產和民用航空領域，裝備了遇險示位標，在其他領域尚未充分使用。如果在海、陸、空各個領域，能夠充分利用全球衛星搜救系統，就可以為人民的生命財產，提供安全保障，更好地為我國的經濟建設服務。我國幅員遼闊，地理條件復雜，經濟發展迅速。特別是改革開放以來，使航海、航空、長途運輸、地質勘探、科學考察、登山探險等經濟活動發展迅猛。而我國目前的地面網絡，還很難做到大范圍的覆蓋，更難以有及時準確的遇除報警和搜救網絡；還有相當多的邊遠地區，甚至還無法建立地面網絡。利用衛星搜救系統，實現遇險的報警和定位，是我國目前在現有技術條件下最有效的全球搜救手段。

SARSAT Statistics：Registered Beacons in the US

NOAA satellites helped save 330 lives in 2021

NOAA’s fleet of advanced satellites are essential for predicting weather and climate, and last year they also helped rescue 330 people from potentially life-threatening situations throughout the United States and its surrounding waters.

Of the 330 U.S. rescues, 195 were water rescues, 29 were from aviation incidents and 106 were from events on land. Alaska had the most SARSAT rescues with 55, followed by Florida with 52 and California with 37. 

NOAA’s polar-orbiting and geostationary satellites are part of the global Search and Rescue Satellite Aided Tracking system, or COSPAS-SARSAT, which uses a network of U.S. and international spacecraft to detect and locate distress signals sent from emergency beacons from aircraft, boats and handheld Personal Locator Beacons (PLBs) anywhere in the world. Since its start in 1982, COSPAS-SARSAT has been credited with supporting more than 48,000 rescues worldwide, including more than 9,700 in the United States and its surrounding waters.

When a NOAA satellite pinpoints the location of a distress signal in the U.S., the information is relayed to the SARSAT Mission Control Center at NOAA’s Satellite Operations Facility in Suitland, Maryland. From there, the information is sent quickly to Rescue Coordination Centers, operated either by the U.S. Air Force for land rescues, or the U.S. Coast Guard for water rescues. NOAA also supports rescues globally by relaying distress signal information to international SARSAT partners.

Among the success stories last year, a miner was rescued from a 20-foot shaft about 30 miles northwest of Phoenix, Arizona, in the Bradshaw Mountains. The Air Force Rescue Coordination Center received the alert from the PLB and contacted the owner, who provided the details of the distress. The Yavapai County Sheriff’s Office deployed a helicopter and emergency medical units to the scene. Rescuers pulled the miner from the shaft and transported him to a Phoenix hospital for treatment of multiple injuries.

“Each rescue shows the SARSAT system works as planned," said Steve Volz, Ph.D., assistant NOAA administrator for its Satellite and Information Service. "Its life-saving ability is built on four decades of teamwork with the U.S. Coast Guard, the U.S. Air Force, NASA and our international partners.” 

By law, beacon owners are required to register their devices online with NOAA. The registration information helps provide better and faster assistance to people in distress, and reduces false alarms. It may also provide what type of help is needed.