diff --git a/edosl0util/eos.py b/edosl0util/eos.py
new file mode 100644
index 0000000000000000000000000000000000000000..c420a944387814fb6b4fb7cd28e4f707be225c97
--- /dev/null
+++ b/edosl0util/eos.py
@@ -0,0 +1,41 @@
+""" NASA EOS mission specific data
+
+References:
+    1. MODIS Command, Telemetry, Science and Engineering Description,
+       Document Number 151840, May 1997, Appendix C
+       https://directreadout.sci.gsfc.nasa.gov/documents/satellite_gen/MODIS_UG.pdf
+"""
+
+packet_types = {
+    0: "day",
+    1: "night",
+    2: "eng1",
+    4: "eng2",
+}
+
+packet_sources = {
+    0: "solar-diff",
+    1: "srca-cal",
+    2: "bb-cal",
+    3: "space-cal",
+}
+
+packets_per_scan = {
+    "day": 3032,
+    "night": 326,
+}
+
+def sourceid(p):
+    if p.data[0] >> 7 == 0:
+        return "earthdata"
+    return packet_source[p.data[0] >> 5 & 0x3]
+
+def mirrorside(p):
+    return ["side1", "side2"][bytes(p.secondary_header)[8] & 0x1]
+
+def scancount(p):
+    return bytes(p.secondary_header)[8] >> 1 & 0x7
+
+def pkttype(p):
+    return packet_types[bytes(p.secondary_header)[8] >> 4 & 0x7]
+