Nadir is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. The term nadir can also be used to represent the lowest point reached by a celestial body during its apparent orbit around a given point of observation. This can be used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The sun is said to be at the nadir at a location when it is at the zenith at the location's antipode
Point-to-Point Protocol over Ethernet longer packets are allowed. Using PPPoEoA with the RFC2684 VC-MUX header option is always much more efficient than the LLC option, since the ATM overhead, as mentioned earlier, is only 32 or 36 bytes (depending on whether this is without or with the ethernet FCS option in PPPoEoA) so that a 1500 byte long packet including all overheads of PPP + PPPoEoA using VC-MUX equates to a total 1500 + 36 = 1536 bytes ATM payload if the FCS is present = 32 ATM cells exactly, thus saving an entire ATM cell. With short packets, the longer the header overheads