AO-40 RUDAK Hardware
AO-40 RUDAK Hardware
The RUDAK project manager and lead hardware designer is Lyle Johnson, WA7GXD.
There are two independent processors, both NEC V53's. The V53 is similar to an Intel 8086, but with integrated I/O functions and the ability to address 16 megabytes of physical memory. Each processor has the full 16 megabytes of memory, arranged as 1 megabyte of program memory and 15 megabytes of solid-state disk. Each processor also has 10 serial ports, and 16 DMA channels.
Each processor has the following modem complement:
Each processor is connected to CEDEX, the two GPS receivers, MONITOR, and the two SCOPE cameras through serial ports, CAN bus, or both.
Each processor can listen to the 400bps IHU telemetry stream.
So, at launch and after a RUDAK reset, we have the current digital satellite standard modulation of 9600 baud FM. We can have many other standards with the DSP modems, including the 1200 PSK standard; and as many esoteric standards as someone wants to write DSP code for.
Each mo and dem (we don't call them modems since the uplink and downlink pieces are completely separate!) can be running at the same time, appearing on the IF passband at different places. The link margins are such that we'll have to use most of the available digital downlink power to support a single 9600 baud downlink, such that the performance into a "standard" 9600 baud LEO ground station from apogee is the same for P3D as it is for KO-23. We can appear on more than one downlink band at a time, however, and can simultaneously support other protocols that are more heavily coded and are at lower baud rates, or high speed downlinks to gateway ground stations with larger antennas.
Of particular interest is the inclusion of a NASA-standard rate-1/2 convolutional forward error correction coder, which is optionally available on one of the high-speed modems. This drops the data rate by 50%, to 76.8 kbps, but provides enough gain from the FEC that it should be possible to receive this data downlink with a modest antenna, modest receiver, and Pentium or equivalent processor running the convolutional decoder. In other words, a really useful data downlink that will be receivable by almost anyone.