| 翻訳と辞書 |
Orbcomm
ORBCOMM () is a company that offers M2M〔(Orbcomm Global M2M Connecting the Worlds Assets )〕 global asset monitoring and messaging services from its constellation of 29 LEO communications satellites orbiting at 775 km. Like its voice-centric competitors Iridium and Globalstar, it filed for Chapter 11 protection, in September 2000. ORBCOMM issued a public offering of stock in November 2006.〔(【引用サイトリンク】title=ORBCOMM Inc.'s 2007 10K )〕 The company sold 9.23 million shares of common stock.
==Satellites==
The first-generation OG1 satellites each weigh . Two disc-shaped solar panels articulate in 1-axis to track the sun and provide 160 watts of power. Communication with subscriber units is done using SDPSK modulation at 4800 bit/s for the downlink and 2400 bit/s for the uplink.
Each satellite has a 56 kbit/s backhaul that utilises the popular TDMA multiplexing scheme and QPSK modulation.〔(), SEC Info〕 Orbcomm is the only current satellite licensee operating in the 137-150 MHz VHF band, which was allocated globally for "Little LEO" systems. Several such systems were planned in the early to mid 1990s but Orbcomm was the only one to successfully launch. In the continental United States, ORBCOMM statistically relays 90% of the text messages within six minutes, but gaps between satellites can result in message delivery times of 15 minutes or more. Orbcomm reported during an earnings report call in early 2007 that 50% of subscriber-initiated reports (messages of six bytes in size) were received in less than 1 minute, 90% in less than 4 minutes and 98% in less than 15 minutes. With the current constellation of ORBCOMM satellites, there is likely to be a satellite within range of almost any spot on Earth at any time of the day or night. Every satellite has an on-board GPS receiver for positioning. Typical data payloads are 6 bytes to 30 bytes, adequate for sending GPS position data or simple sensor readings.
A total of 35 satellites were launched by ORBCOMM Global in the mid to late 1990s. Of the original 35, a total of 29 remain operational today, according to company filings. The plane F polar satellite, one of the original prototype first generation satellites launched in 1995, was retired in April 2007 due to intermittent service. Two additional satellites (one from each of Plane B and Plane D) were retired in 2008 also due to intermittent service. The other five satellites that are not operational experienced failures earlier. The absence of these eight satellites can increase system latency and decrease overall capacity. Orbcomm has invested in replacement satellites as the first generation is at or nearing end of life. On 19 June 2008 six additional ORBCOMM satellites were launched with the Cosmos-3M rocket:〔(【引用サイトリンク】title=Russia's Cosmos 3M rocket blasts off with six U.S. satellites )〕 one ORBCOMM CDS weighing 80 kg, and five ORBCOMM Quick Launches weighing 115 kg each.〔(OHB-System milestones )〕〔(OHB-System missions )〕 These new satellites were built by German OHB System AG (platform) and by Orbital Sciences Corporation (payload) and included a secondary AIS.〔()〕〔(Orbcomm failures )〕 Design and production of the satellite platform was subcontracted by OHB System to Russian KB Polyot. On November 9, 2009 ORBCOMM filed a report to the United States Securities and Exchange Commission stating that since launch, communications capability for three of the quick-launch satellites and the CDS has been lost.〔http://www.sec.gov/Archives/edgar/data/1361983/000095012309059834/c91352e10vq.htm〕 The failed satellites experienced attitude control system anomalies as well as anomalies with its power systems, which resulted in the satellites not pointing towards the sun and the earth as expected and as a consequence have reduced power generation. The company has filed a $50 million claim with its insurers covering the loss of all six satellites〔http://www.spacenews.com/satellite_telecom/091113-defective-satellites-hobble-orbcomms-ais-business.html〕 and received $44.5 million in compensation.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Orbcomm」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|