## Name

orbsos - compute SOS coordinates from an orbit

## Synopsis

orbsos in=orbit [parameter=value]

## Description

orbsos will compute the Surface of Section (SOS) coordinates from an orbit. Currently one can only do this for 2D orbits, in the x-y plane. There is an option to compute the X-VX or Y-VY SOS coordinates.

The output is a simple ascii table with 4 columns: number, time, position and velocity. Example of use with tabplot(1NEMO)

```    % orbsos orbit.out x | tabplot - 3 4 xlab=x ylab=vx
% orbsos orbit.out y | tabplot - 3 4 xlab=y ylab=vy
% orbsos orbit.out x,y | tabplot - 3 4 xlab=x,y ylab=vx,vy
```

orbsos can be useful in locating unknown orbital families. Finding periodic orbits can be automated, but is easier through programs like perorb(1NEMO) and henyey(1NEMO) .

## Parameters

The following parameters are recognized in any order if the keyword is also given:
in=in-file
Input file, which must be an orbit(5NEMO) . [No default].
mode=x|y|x,y|
Mode to tabulate. x computes the x-vx, and y computes the y-vy SOS coordinates. [default: x].
pabs=t|f
Compute absolute values in the surface of section position coordinate? Only useful for non-rotating potentials. [Default: f]
vabs=t|f
Compute absolute values in the surface of section velocity coordinate? Usually useful, as a surface of section is symmetric w.r.t. to the position axis. [Default: f]

perorb(1NEMO)

Peter Teuben

## Files

```~/src/orbit/misc     orbsos.c
```

## Update History

``` 9-jun-88    V1.0 Created      PJT
22-mar-92    V1.1 added mode= and documented      PJT
30-dec-93    V1.2 added pabs= and vabs=    PJT
```