Some Mission-specific notes for MAKI

General Euler Angle Notes

Definition of Spacecraft and Sky Axes

Sun limits are maximum deviation of sun and spacecraft Y axis.

Sun Angle minimum and maximum are the range of sun angles for the Z axis.

For calculating rolls, we use Euler angles. We convert RA and Dec to Euler Phi and Theta, then calculate rolls.

For Euler angles and Sun angles, the Y-axis is perpendicular to the solar panels, the X-axis relates to the roll angle, and the Z-axis defines the boresight.

Roll Angles

For all missions, the roll angle is defined in X-ray sky images ("look-up" direction); increasing roll angle corresponds to a counterclockwise rotation of the FOV.

The detectors are mapped out in terms of the Spacecraft +X and +Y axes within the code, then projected onto the world coordinate system.

Adding a new mission or new FOV

To add an FOV to WASABI, simply email the WASABI user's list at wasabi@athena.gsfc.nasa.gov and provide the detector layout in units of decimal degree FOV, where +x is the spacecraft +X axis and +y is the spacecraft +Y axis. Include also what the nominal center pointing (on-axis pointing) reference coordinate is. This center is where placed FOVs will (of course) be centered, and will also serve as the rotation point when investigating roll.

Specific Mission Details


For Astro-E, the long side of the XRS array is set to align with declination, so that the roll angle corresponds to the ISAS "jcoord" software.


For ASCA, we use the additional definition that roll=0 corresponds to the spacecraft Y axis physically pointing west. Note, however, that the X-ray telescopes used for these missions invert the images, hence the X-ray image will have the Y axis pointing east for roll=0.

Sandy Antunes
Dr. Lawrence Brown
Last modified: Wed Jul 7 11:40:12 EDT 1999