Source:  http://cr4.globalspec.com/thread/29317#newcomments

 

Hello Members,

Please go through this BBC story of the Chinese built/launched communications satallite for the Nigerian government. Here http://newsvote.bbc.co.uk/2/hi/africa/7726951.stm

The satellite was launched about two years ago and it is confirmed packed up.

Apart from the indicated power problem, what could be other causes of the satellite failure?

Cheers,

ethobil

 

Observations

The BBC article stated that the Nigerian satellite

1. … was limited because the type of frequency it used was disturbed by clouds in the atmosphere, and did not work properly in Nigeria’s rainy season or during the Harmattan, when clouds of dust blow down from the Sahara, he said.
2. … also operated on frequencies already allocated to other companies and interfered with other providers’ equipment.
3. … controllers shut the satellite down because it was having problems with its power supply, the government announced.

The observations in #1 and #2 are items that I learned to look out for before I graduated with my Bachelors.

Background for Observation #2:  Operating a satellite on another satellite’s frequency is both extraordinarily rude and stupid.  Interference from the satellite assigned that frequency will make both satellites useless for significant portions of their design life.  Obviously this is to be avoided and there are agencies to regulate these frequencies.

Background for Observation #1:  This is amatuer hour stuff.  Anyone with satellite TV or satellite radio knows that weather interferes with transmissions.  The thing is, the impact of weather can be minimized if not eliminated if you pick the correct frequency.

You may be asking why I addressed #2 first and then #1.  The answer is this, Observaton #2 shows that the Nigerians didn’t do even the most basic homework and contact the proper authorities.  Observation #1 reinforces this notion through an ignorance of basic satellite operations and limitations.

Observations #1 & #2 demonstrate that on the Nigerian customer (at least those in charge) didn’t know the first thing about what they were buying.  Questions about operations, lifetime, and weather are pretty basic and I learned to ask those questions before graduating with my Bachelors.

The final Observation

Observation #3 is that the satellite was shut down for power problems.  This could be something like a battery failure, power subsystem failure, solar array failure, or ADCS failure (which could point the arrays or the whole satellite the wrong way).

Given that the Nigerians didn’t do their homework – to know which frequency to use for their communications satellite, nor did they do enough homework to contact the correct regulatory agencies – before buying an expensive piece of hardware it only makes sense that they didn’t do their homework regarding system testing.

My guess is that the Chinese bid cheap re-using a satellite they designed for someone else.  This is common practice to reduce cost and risk.  But there are always custom changes when requirements change or new, updated hardware is added to the design.  If you don’t test the integrated system properly the chances of failure are high.  The Nigerian satellite was probably a recycled telecom satellite from another customer and some component of power system (like bateries) or the ADCS system (like attitude sensors or thrusters) was replaced.

An example of what I’m thinking…

An ADCS sensor, lets use a gyro for now, is replaced.  The new sensor comes from the same manufactuerer with the same power, size, and mounting requirements.  However, this new sensor provides its output in a different coordinate system such that 2 of the 3 axes (X & Y) are identical to the previous sensor but the 3rd axis (Z) is -1 of the original.  Without thorough design effort and proper integrated system testing, this -1 is easy to miss.  Then the whole satellite ends up pointed away from the sun and runs out of power.

The Nigerians missed the easy stuff, why would we assume they got the hard stuff, like proper testing, correct?