diff --git a/src/wcs.ts b/src/wcs.ts
index 2dbf5cf..481e816 100644
--- a/src/wcs.ts
+++ b/src/wcs.ts
@@ -1,11 +1,25 @@
 /*****************************************************************************************************************/
 
 // @author         Michael Roberts <michael@observerly.com>
-// @package        @observerly/astrometry/vsop87
-// @license        Copyright © 2021-2023 observerly
+// @package        @observerly/astrometry/wcs
+// @license        Copyright © 2021-2025 observerly
 
 /*****************************************************************************************************************/
 
 export type {}
+/*****************************************************************************************************************/
+
+// SIP (Simple Imaging Polynomial) is a convention used in FITS (Flexible Image Transport System)
+// headers to describe complex distortions in astronomical images. It extends the standard World
+// Coordinate System (WCS) by introducing higher-order polynomial terms that account for non-linear
+// optical distortions, such as those introduced by telescope optics or atmospheric effects.
+// @see https://fits.gsfc.nasa.gov/registry/sip/SIP_distortion_v1_0.pdf
+export type SIP2DParameters = {
+  AOrder: number
+  APower: { [key: string]: number }
+  BOrder: number
+  BPower: { [key: string]: number }
+}
+
 
 /*****************************************************************************************************************/
diff --git a/tests/wcs.spec.ts b/tests/wcs.spec.ts
new file mode 100644
index 0000000..e69de29