FA-69453 / Orbital propagation / Member archive

Two-line element set line 1: Negative BSTAR loses its sign · case 03

Negative drag terms become positive.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input one TLE line-1 string (exactly 69 characters, starting "1", else None). Epoch year from columns 19-20 (57-99 -> 1900s, 00-56 -> 2000s), epoch day 21-32, ndot/2 34-43, BSTAR 54-61 in assumed-decimal exponent form (" 34123-4" = 0.34123e-4, sign first), checksum column 69 (digits plus 1 per "-", mod 10). Return [year, day, ndot2, bstar rounded 14, checksum_ok].

Why this case matters

Orbit determination and mission planning chain many small conversions; one wrong branch or unit silently moves a spacecraft by kilometres.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
two-line element set line 1 "1 25544U 98067A 08264.51782528 -.00002182 00000-0 -11606-4 0 2927"	`[2008, 264.51782528, -2.182e-05, 1.1606e-05, true]`	`[2008, 264.51782528, -2.182e-05, -1.1606e-05, true]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.