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A sun outage happens when the solar radiation (better known as sunlight) from the sun distorts or interrupts the signals sent by geostationary satellites. It is also known as a sun transit or sun fade. Its effects can range from slowing down or disrupting satellite TV, internet, and phone connections, to cutting off the telecommunications of an entire island, to affecting the economy of a subcontinent.
As anyone familiar with Galileo knows, the earth orbits the sun. And at certain times in the year, the path that the sun takes in the sky sometimes puts it right behind the line of sight of an earth station and a satellite. These are called sun transits.
Now, being a controlled and sustained fusion reaction well past the five-billion-year mark, the sun gives off powerful radiation across the entire spectrum. This includes the visible, ultraviolet, infrared, and microwave ranges.
Satellites happen to communicate through three microwave frequencies: C-band, Ku-band, and Ka-band. These bands get swamped by the microwave energy given off by the sun during sun transits. When this happens, the satellite cannot communicate with the earth station. This disruption is called a sun outage.
Sun outages only affects downlinks from satellites. Uplinks from the Earth are usually unaffected.
Also, the orbit of a satellite determines the extent of the solar outage’s effect. Satellites in geosynchronous orbit are affected based on their inclination vis a vis the Earth and the Sun. Satellites in other orbits are frequently affected, but the effects are brief.
Sun outages sweep from north to south starting around February 20 up to April 20. They sweep from south to north starting around August 20 and ending around October 20. A typical sun outage lasts for less than 12 minutes, and there will only be one such occurrence per day. Sun outage seasons can run up to two weeks.
Countries and cable companies give out warnings about predicted sun outages that will disrupt satellite communications. Most incidents are minor annoyances. But sun outages can also cause serious consequences.
The British territory of Saint Helena is one of the most isolated places in the world. The remote South Atlantic island is only physically accessible by boat so far. It relies on a single teleport to handle its entire telecommunications traffic. When a sun outage hits, the entire island and its population of 4,550 people are for all intents and purposes cut off from the world.
The country of India is even more greatly affected by sun outages. The members of the Bombay Stock Exchange and National Stock Exchange use VSATs to connect to their trading systems. VSATs rely on satellites to connect their terminals, and sun outages will disrupt those connections. And if the transmission of data during online transactions is disrupted, it may ruin the deals and cost money.
To protect against such disruption, the two Indian stock exchanges normally close from 11:45 AM to 12:30 PM during sun outage season. The BSE and NSE’s working hours would also be extended to make up for the time lost during the sun outage. The government had also encouraged stock exchange members to use alternatives to VSATs that are unaffected by sun outages.
India’s DTH market needs to source satellite capacity from foreign satellite carriers to sustain its growth. Members of the Cable & Satellite Broadcasting Association of Asia appealed to Asian government to ease protectionist policy to satisfy pent-up market demand. According to Simon Twiston Davies, chief executive officer of CASBAA , the local digital telecommunications and DTH markets, despite the ISRO success, remained under-provisioned.
The local industry cannot meet the demand from commercial satellite services and DTH network operators. Deregulating the market to make international partnership possible is therefore essential to ease the shortage in transponder capacity. The Office of the US Trade Representative (USTR) can’t help but agree. The agency lashed out China and India for their refusal to comply with open-trade policy when it comes to domestic satellite communications industry.
India has scheduled up to four space launches in the next year, including two crucial tests of the Geosynchronous Satellite Launch Vehicle, a medium-class rocket envisioned as the cornerstone of Indian ambitions for fully independent access to space.
The chairman of India’s space agency, K. Radhakrishnan, announced the preliminary rocket manifest last week following the successful launch of a Polar Satellite Launch Vehicle with a radar surveillance satellite.
The PSLV has achieved a success record of greater than 90 percent in 21 launches, but India’s larger rocket - the GSLV - has been grounded since 2010 following a string of failures.
The Indian Space Research Organization has declared four failures in the GSLV’s seven launches.
The countdown for the Thursday early morning launch of a rocket laden with remote sensing satellite Risat-1 has begun in Sriharikota in Andhra Pradesh, an ISRO official said, a step that will reinforce India’s global leadership position in the field.
The indigenous Radar Imaging Satellite (Risat-1) would be used for disaster prediction and agriculture forestry, and the high resolution pictures and microwave imaging could also be used for defense purposes, a statement from Indian Space Research Organization (ISRO) said.
Polar Satellite Launch Vehicle (PSLV) is all set on the launch pad at Sriharikota, 80-km from here, to blast off at 5.47 am on April 26 ferrying the 1,858 kg Risat-1, a wholly Indian-built spy/surveillance satellite. “
(Source: New York Daily News)