Posts Tagged ‘satellite outage’

What’s This Button For?

Thursday, September 15th, 2011

In spacecraft operations, the last thing you want is a ground controller who decides following the standard operating procedure is for idiots. Not sure if that’s what happened at the Ciel-2 TT&C facility, but something bad did, causing the spacecraft to go into safe mode.

The customer, DISH Network, leases capacity from SES, who leases from Ciel Satellite Group, owners of the spacecraft, acknowledged the anomaly…

DISH Network restored all affected television channels for its customers Wednesday morning after experiencing a temporary interruption of service on some of its channels overnight.

The interruption mainly affected high definition channels to a portion of DISH Network customers. Standard definition channels were largely unaffected resulting in a majority of DISH Network customers not being affected at all.

The interruption began at approximately 5 p.m. ET Tuesday and involved the Ciel2 satellite, which is operated by SES at 129 degrees West Longitude through a Canadian subcontractor and leased to DISH Network. SES has attributed the anomaly to human error in its ground operation of the spacecraft. According to SES, there is no issue with the health of the satellite.

I’m glad I’m in the eastern arc and unaffected by this outage. I feel sorry for the folks in Saskatoon — those who committed the “human error” in question. The spacecraft lost its orientation and therefore automatically went into safe mode, a near total shutdown. Afterwards, it take a few hours to turn on the tubes.

DIY Friday: Sun Outage Calculator

Friday, February 23rd, 2007

There is no greater tool for DIY enthusiasts than the Internet, and today’s DIY activity is just a click away: a sun outage calculator!

But wait — what’s a sun outage? Now’s a good time to ask.

Sun outage is a natural phenomenon, which occurs twice a year (in the spring and fall) when the sun appears to be passing directly behind the satellite as seen from a receiving earth station.

Since the sun is a potent source of radio frequency energy, the earth station’s receivers are overwhelmed by the sun’s “noise” output and reception becomes impossible for a brief period of time, usually less than 10 minutes.

An observer at the earth station will notice that the antenna feed’s shadow will fall exactly in the center of the reflector during the peak of the sun outage period.  This indicates that the antenna, the satellite and the sun are in direct alignment.  At this point in time, the sun’s radio signals are being focused directly into the antenna’s receive feed.  This results in a temporary degradation in the signal to noise ratio of the signal being received from the satellite and a consequent degradation in Eb/N0 (Energy per bit over Noise referenced to zero) in digital systems.

Sun outage generally occurs between 9 AM and 3 PM for locations in the continental United States.  The duration and intensity of the outage will begin as a slight degradation in signal, increasing to a peak level over several days and will then begin to reduce in intensity and duration over a similar period.  These outages pose no danger to earth station equipment and they are not related to sunspot activity.

So how do you predict when the sun is going to mess up your signal? This sun outage calculator gives you predictions based upon the satellite you’re receiving from, your location on earth, and the time and date.

SES also offers a bunch of charts (good luck with that). Intelsat also offers marginally useful maps of sun outages for spacecraft — but they let you input your exact location. I like that.