celebration of cosmic touchdown by European Space Agency

The European Space Agency celebrated a cosmic touchdown Wednesday by successfully landing a spacecraft on a comet for the first time in history. The agency said it has received a signal at 1603 GMT from the 100 kg Philae lander after it touched down on the icy surface of the comet named 67P/Churyumov-Gerasimenko. While further checks are needed to ascertain the state of the lander, the fact that it is resting on the surface of the speeding comet is already a huge success. It marks the highlight of the decade-long Rosetta mission to study comets and learn more about the origins of these celestial bodies. The head of the European Space Agency underlined Europe’s pride in having achieved a unique first ahead of its US counterpart NASA. “We are the first to have done that, and that will stay forever,” said ESA director-general Jean-Jacques Dordain. The landing caps a 6.4 billion-kilometer journey begun a decade ago. Rosetta, which was launched in 2004, had to slingshot three times around Earth and once around Mars before it could work up enough speed to chase down the comet, which it reached in August. Rosetta and the comet have been traveling in tandem ever since at 66,000 kph. The comet was discovered in 1969.

XOR gate using tranistors

the circuit below is the transistor xor gate and the led will glow only A and B inputs are opposite to each other. this is very important circuit used in making adder circuit and other very important device. this circuit is successively simulated in proteus simulator and is tested successfully. please check it out to improve your practical knowledge in logic circuit.