Celestia Forums

Hi,

Is the Lua interface in Celestia able to handle bitwise operations for data transmission? I'm thinking of data encapsulation like in the PUS standard.
If I remember correctly separate libraries have to be included into the standard version of Lua to do so.

Is this possible within Celestia?
I think most of the communication between a ground station and a spacecraft is based on PUS to create data packets.

Has anybody used this in any kind of way?
I would use it for communication between a simulator and Celestia.

Thanks in advance
Stuffer

Stuffer,

I don't know about the interface with Celestia but I think you're correct. From what I read in the following links, the bitwise operators are not available in std LUA, but only via a separate library:
http://lua-users.org/lists/lua-l/2007-10/msg00764.html
http://www.wowwiki.com/Lua_functions (near the bottom)
http://www.gammon.com.au/forum/bbshowpost.php?bbsubject_id=4907


I did find this statement intriguing at the bottom of the 3rd reference above:

The bitwise operations are now conducted after converting the internal "double" (floating point) Lua numbers into 64-bit integers. Internally doubles are stored as 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa. Their range is +/–1.7E308 with at least 15 digits of precision.

I don't know anything about the "PUS standard", but this statement seems to suggest that a workaround might be possible by passing "doubles" and then converting in Celestia, in order to perform bitwise operations.
I suspect this is not quite what you need, but may help.

CC

Was curious about PUS myself, especially since it was stated it involved satellite telemetry.
PUS = Packet Utilization Standard

Found a few links on the subject:
THE ECSS PACKET UTILIZATION STANDARD AND ITS SUPPORT TOOL
PUS Upgrade of the Columbus Ground System (CGS) for Satellite Check-out
Package Declaration of PUS Data Types
A Powerpoint presentation: ECSS E-70-41: Telemetry & Telecommand Packet Utilisation

Additional more recent sources can be found with Google searches of things such as "ECSS packet", "CCSDS packet", and "uplink packet" or "downlink packet". Interesting

Hi

Does anyone of you guys know, how to integrate a external library into Celestia?
I'm not familiar with Celestia's source.

I also use sockets for the connection and the integration of the socket library was quite simple. Is it the same with any library?

Thanks
Stuffer