Navigation and Ancillary Information Facility (NAIF)






Q. What kind of SPICE kernels should I prepare ?

A. FLOW is an FOV simulator, so you have to prepare kernels to determine FOV. Normally, SCLK, SPK, FK, and IK are required. Technically, you must prepare SPICE kernels to call 'getfov_c' and 'pxform_c' functions.

Q. Can I make a movie using this tool ?

A. No. This tool can only output a still image at a time. In the configuration file, you may find 'time_start', 'time_end', and 'time_step', and you probably think these options are available to make a movie. But actually, these options are prepared to simulate a push-broom scanner.
If you want to make a movie, you have to make lots of images using another script like below:
use Time::Local;
$t = timelocal(0,23,14,13,11-1,2009); # 2009-11-13T14:23:00
for($i=0; $i<60; ++$i) {
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($t);
$iso = sprintf("%04d-%02d-%02dT%02d:%02d:%02d.%03d",
$filename = sprintf("%04d.png",$i);
`flow_se color_rosetta.lua -t $iso | flow_ig -o $filename`;
$t = $t + 1;
then, make a movie using your favorite tools such as iMovie, Windows Live Movie Maker, ffmpeg, etc.

Q. An image is generated, but it is a black image. Is this correct ?

A. That depends. If your FOV simulation is a simulation in the night side on a planetary surface, your black image might be correct. If so, try 'flow_ig -x ge_disable_light'. The 'ge_disable_light' option have the simulation ignore shadow effect.
If you know the condition well and it should not be a black, check the 'output_objects' part of the configuration:
output_objects = {
If these objects are not defined correctly, "flow_ig" outputs a black image.


Q. Can I use SPICE meta-kernel in my configuration file ?

A. Yes, you can use SPICE meta-kernel in the configuration file like below:

spice_kernels = {

important STAR catalog kernels, such as 'hipparcos.bdb', cannot be included in the meta-kernel. You have to specify a STAR catalog kernel in the configuration file independently.

Q. Why should I use separate setting for satellite spk kernels ?

flow_se searches satellite names ("SATELLITE.<name>" in the configuration file) only from the SPICE kernels listed in the satellite_kernels. Technically, their kernels are the first argument to spkobj_c().


Q. Where can I find planetary textures ?

A. You can find a planetary texture using search engine easily. The keywords are "planetary texture".
important You have to be careful about the copyright of the textures.

Q. Can I use SPICE DSK shape model ?

A. The SPICE DSK type 02 is implemented, but still experimental.

Q. The planetary surface looks different between a real picture and FLOW's output.

A. You have to check the coordinate of the source texture. The left edge of the texture must be at longitude 0 degrees. Please see the Appendix for more detail.


Q. What is "flow_se: (config file error): attempt to call a string value" ?

The message indicates the configuration file is somthing wrong. It often occurs in the following cases:
  1. No comma after an item in the list (the following example, comma is required after "kernel2")
  2. spice_kernels = {
  3. Broken pair of brace (The following example, close brace is missing)
  4. object_table = {
    ["PLANET.EARTH"] = {
    type = "texture-body",
    file = texture_file_dir .. "earth.jpg",
  5. Missing single/double quotes (The following example, close double quotes is missing)
  6. time = "2009-11-13T14:23:00

Q. What is "unknown image format for file abc.jpg" ?

The message indicates your compilation of "FLOW" is failed. Using JPEG format as a planetary texture, your operating system must have jpeglib and its headers, and libraries when compiling the "FLOW". Even if jpeglib is not installed in your system, compilation will successfully finish, but the output "flow_ig" does not support JPEG format. As well as PNG or FITS, you have to install libpng or CFITSIO respectively in advance. You can check the supported options with the following command:

$ flow_ig -V
flow_ig version 1.1
    JPEG support ... yes
    PNG  support ... yes
    FITS support ... yes
    WMS  support ... yes
    DSK  support ... yes