Monday, July 4, 2016

LEO Satelite-1

LEO SATELITES
Recently few engineering students publicized that they made a CUBE satelite and put into theorbits with help of ISRO. Their website is at http://www.coep.org.in/csat/   they described their tale, their institue is very proud, they got many appalause from lots of politicians, dignitaries their fair share of 5 minutes fame. Wow our kiddos did great things.

But, there were few critical voices, who analyzed and considered that in europe and amerika this cube satelite project kits is freely available and ours did not differe. Few friends requested COEP to provide the close up image, ckt diagrams , details of satelite but it is not revealed.  Lots of geeks pointed out the anamolies in signals uplink downlink maintenance of ground stations etc. In those opinion it seems it was a hobby project in big propotionals where every one is happy except the end users. We the ham.

In this entire project the ground station relaity were never considered. Freq used is in UHF. How many hams have ful fledged VHF,UHF stations capable to cath up the birds ? very few. Modulations is FM BPSK , which is very wrong due to doppler shift. Even the pure carrier on-off cw might have been good. 

Ground stations needs some yagi beam antenna. Now a days dongle is available and with computer software we can decode many modes and of course cw also.

I raised the question, how many hams, or ham bodies were consulted before making the project ? Ham resources are free but limited. Atleast any institutions making any project should put their proposal, ask for guidance , opinions to groups of hams, institutions, clubs , experts etc however they are not legally required to do so. If you make something which is not usable to the end users ( we hams or any students, common man then what is need of blocking one space in LEO, making hue cry, spending 7+27 lacks money. India is a poor country and we do not have luxury to spoil resources. LEO orbitt is already full of scraps why put more SCRAP ...
Anyway enough of oil-burning.  The life time of this satellite is only 6 months to 1 year and it will be history. Forget them and Now lets go to technicalities in simple terms.

CUBE SATELITE

your can buy ready made from CubeSatShop.com

Cube satelite is just a simple cube. outer surface contains the solar panels. Batery,4watt. It might have antenna, becon, transponders ( budged ?), camera, azimuth level control , sun sensor, communications channel. on board computer etc.
 
The main problem is to fit all this elements of our choice into a small size cube without increasing weights. Second is fabrications. It need precise engineering. Wth advent of CNC, 3D printing it has become easy. All material should be radiation hardened.

If you have enough money every thing is cheaply available off the shelf and ready made in amerika, Europe.

ORBITS
 We are used to poing our dish antenna to the satellite and receive TV, NEWs Entertainment. They are in Geo-statitonary orbit. Antenna remains constant. Satelite and earth moves with same speed. But LEO satelites does not give constant view. It moves around earth in elliptical orbit. Its speed and earths are different. At one point they are very near to the earth 300 km and at other point they are far /1200km . So, when they are near we can receive good, work them with very low power transitters. If they are very far from us they become useless.  We choose this orbit due to low budget, easy of ground stations connectivity, low cost equipment, easy to put into orbit ( rides on some big rockets at no real cost.) and we can make it at our school, home with easy.

ORBITRON 

How do we know when satellite will pass near our place ? There is a software which predicts where our satelite in interest is. All satelites are being monitored by amerikan NORAD. We can download the latest data from their website. As many forces takes place and our satelites do not have boosters, fuel rockets to correctly maintain its course they are constantly being monitored by USA.  Every object in the space is given a SSN number.
 

Best software ORBITRON is from our own ham xxxxx ,he made it when he was just a kid. Better than indian kids. Anyway from his website get a zip file. There will be 32bits , 64 bits system also. ZIP are non-install type which works without any installations, good for many fricking new computers which requires fucking micro-hards software signature verifications certificates ( linux is good to opern source and hams).

RECEIVER -Decoding Software.
 
Hams use all mode FT897D. Its compact & best rig for portable use. and it operates from HF to VHF,UHF. But, it is costly.

On cheap side, It is reported that dongle is also good with SDR sharp software. It can decode the signal.  Actually you need a yagi, receiver, the base band file to be decoded by software..... or yagi, dongle, computer, software and everythign is fine.

ANTENNA
 
Put a simple yagi pointing up into the sky, try to see in computer. As actuall pass is very short.
 
Consider the satelite as bird. If a bird is flying above your head, you will be seeing it coming near you, over your head and then going afar. The same thing happens. To identify the birds you need to let it come into the visual range. Same thing calles as foot print of satelite.
 
For new hams---As listenign satelites requires some practical guidance, you got to ask clarifications from somehams who has recently worked these satelites.

HAMS

In the past it seems many hams have reached to the sky. have a look. http://www.qsl.net/vu2msy/satellite/vu2rm_satellite_article.htm  In my opinion our VU2MUE has done good works on satlites, APRS, digital communications. He is at Delhi, look out to his website and facebook page for more informations. There are many other professional who worked with NASA, AMSAT organizations i.e VU3GEK, ganeshan, in fact he is a good in sat tech. And many more

FURTHER READINGS

Also do not forget to look up on qrz.com hamuniverse.com, qsl.com   they have good informations. There are dedicated websites also.
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