Talk:SPACEWAY-1

From Wikipedia, the free encyclopedia

I don't think this article benefits from the detailed discussion of the known precision of the spacecraft's weight. I'm pretty sure its weight is precicely known (it's important info for launch, orbit raising, for attitude control)... but Boeing decided three significant figures were sufficient for a press release. In any case, it will be soon be irrelevant [1]. —Fleminra 02:14, May 26, 2005 (UTC)

[edit] change back to Gps for bandwidth from guess of GHz since this is a broadband satellite, note that 500 MHz is the capacity mentioned above

Spaceway 1 is a broadband satellite capable of using its 500 MHz in the Ka-band to achieve a 10 Gps throughput of bandwidth capacity. Even though it is transmitting an RF signal on a second 500 MHz, it is not really a data carrying signal and will be turned off once DirecTV 10 or 11 is placed in the same orbital slot to make use of that second 500 MHz Ka-band frequency range. So 10 Gps is correct for the bandwidth and 500 MHz is the transponder capacity, not 10 GHz.

[edit] bandwidth meaning

"(just take it out, then. If it is supposed to be channel capacity of 10 Gbit/s or something like that, change "bandwidth" and use standard symbols)"

Bandwidth is usually defined as capacity which is 10 Gbps as mentioned in the following original specifications: http://www.boeing.com/defense-space/space/bss/factsheets/702/spaceway/spaceway.html http://www.comlinks.com/satcom/spacew.htm

Bandwidth is different from channel capacity. Bandwidth is similar to an ethernet or ATM switch's backplane capacity while channel capacity is similar to the ethernet port or interface port speeds. The aggregate port speeds would usually exceed the overall capacity of the backplane due to design assumptions about statistically multiplexing of ports.

This may be irrelevant to Spaceway 1 since it is being used as a bent-pipe satellite for high definition transmissions and its regenerative digital switching payload is not really being used for internet communication. This discussion is relevant to the article on Spaceway 3. The article on Spaceway 2 would also need to be updated to be consistent with whatever direction is taken on Spaceway 1's use of the term "bandwidth".

Channel capacity is also complicated by Spaceway's use of uplink spotbeams with frequency subband reuse (and reuse of channels in each uplink spotbeam).

Using traditional bent-pipe transponder based terms makes it difficult to apply to these new broadband satellites...