Is it possible to change the radiosity in sapien or guerilla, i don't have a 3d edittor. If so, what would be a good setting for an odst-like environment (at night ofcourse)

If you want to change your lighting without modifying the contents of the bsp, there are many options.
In Guerrilla, you can change the skybox you want the map to be lit by, as well as the lighting properties of that specified skybox. For example, I used a heavily modified version of the clear afternoon skybox to light Pitfall.
Sapien has a "radiosity paint" feature that bungie disabled for use. So don't ask about it.
In Sapien, it is also good to place device lights and scenery that gives off light in ares you want lit up. You can tweak the light properties of those light devices in sapien, and you can tweak the light properties of other objects in Guerrilla.
It is very difficult to get good results without bsp modification, but I hope these tips helped somewhat.

You could use a night sky with device_lights placed to create pretty lighting (similar to the lights in the exterior of a50). Once placed, you must run radiosity in Sapien in order for the lighting to appear as such. To do so,

1) In Sapien, hit the tilde button (~/`) to open the console, much like you would ingame
2) Type in:
radiosity_quality 1
if you want high quality lightmaps. Else, for debugging purposes, you could use:
radiosity_quality 0
3) Type in:
radiosity_start
to begin lightmaps.

NOTE: THIS WILL TAKE SOME TIME. The screen may freeze, or turn white. It is imperative that you do NOT alt tab out to access another program. This will cause Sapien to stop responding, or at the very least, stop lightmaps from running. After some time, three numbers will appear, and begin counting down to 0. When the three numbers reach 0, type in:
radiosity_save

If you are not running final lightmaps, USE TOOL. It will save a ton of headache.

tool lightmaps levels\level\level level 0 0.9

You can do whatever you want while this runs, and it finishes faster.

i agree with that guy ^^ sapien does a better job quality wise when you type radiosity_quality 1 but tool is soooooo much faster and easier

okay thanks guys. And 0.9 or 1 will be a good setting for an odst-like atmosphere?