Tools
Two small tools. Both run entirely in your browser: nothing you type is sent anywhere.
Client-side only. The page’s Content-Security-Policy forbids connections to anything but this origin and forbids form submission; the scripts contain no network call. The Alpha-5 implementation is checked against the corpus’s specification vectors, which you can re-run here.
Alpha-5 encoder and decoder
Type a catalog number (like 100000) to see its five-character lettered form, or type a lettered field (like A0000) to get the number back. The rules are strict: capital letters only, never I or O, nothing above 339999.
Space-Track’s definition, applied strictly: A=10 … Z=33, I and O skipped, capitals only, exactly five characters; numbers below 100000 are five zero-padded digits; nothing above 339999 encodes. Lenient decoders (python-sgp4’s accepts I, O and lowercase) disagree with strict ones on such inputs, which is why the corpus treats them as invalid.
Examples:
Letter table
| letter | value | catalog numbers |
|---|
(official examples, boundaries, skip boundaries, below-100000 forms, invalid fields and unrepresentable numbers from corpus v0.1.0)
Anatomy of a TLE
A TLE is two lines of exactly 69 characters, sometimes with a name line above. Every position has a meaning. Hover over, tap or tab through the coloured fields to see what each one is. The first example is the one printed in the international standard; the second is the test kit’s lettered rendering of catalog number 100000.
Column layout per CelesTrak’s format documentation; checksum recomputed; the catalog field decoded with the strict Alpha-5 rules; exponent fields decoded from their implied-decimal form; the epoch resolved through the 57 pivot. Presets: the CCSDS annex G example rendered by the corpus renderer, and the corpus’s published derived Alpha-5 line (SARAMAGO, first record).
Paste your own
Paste a TLE (two or three lines). It is checked and taken apart right here in your browser and never leaves this page.
Parsed in the browser: line lengths, both checksums, catalog-field agreement between the lines and strict Alpha-5 decoding. Not sent anywhere; see the CSP in the response headers.