radar ranging
==Yes, radar ranging is extremely accurate for planets and solar system objects==, providing precise distance, velocity, and surface details by timing radio wave echoes, even penetrating thick atmospheres like Venus's to map hidden features and significantly improving orbital predictions for asteroids and planets. Earth-based radars (like Goldstone) and orbiting spacecraft radars (like Magellan for Venus) offer insights into geology, internal structures, rotation, and precise orbital parameters, crucial for planetary science and hazard mitigation.
Astrometric Parallax Pipeline for NEO Distance Measurement (from massive info dump.md)¶
A distributed network can measure the distance to a Near-Earth Object (NEO) directly using geometric parallax — no radar required. This is the optical analogue of radar ranging.
Principle: Two telescopes separated by a known baseline observe the same NEO simultaneously. The NEO appears at slightly different positions relative to background stars in each image. This angular shift (parallax angle p) combined with the baseline distance B gives the object's distance via: D = B / (2 * tan(p/2)) ≈ B/p for small angles.
5-Step Pipeline¶
| Step | Action | Technical Requirement |
|---|---|---|
| 1. Synchronisation | Image the target simultaneously from at least two nodes (T_A and T_B) | GPS-disciplined NTP; millisecond-level sync |
| 2. Astrometric Calibration | Plate-solve both images to determine exact WCS and pixel scale | Astrometry.net or ASTAP on every submitted FITS |
| 3. Baseline Calculation | Determine the exact geocentric distance between the two telescopes at exposure time | GPS coordinates of each node + spherical trigonometry |
| 4. Angular Shift Measurement | Measure the NEO's position in both images relative to distant non-moving reference stars/quasars. The difference is the parallax angle p |
Specialised astrometry software (Astropy, or dedicated pipeline) |
| 5. Distance Calculation | D = B / p (small angle approximation) | Script logic; straightforward arithmetic |
Timing requirement: Millisecond-level synchronisation (GPS-disciplined NTP) is sufficient for this measurement. Microsecond-level timing is only needed for LEO debris triangulation.
Baseline requirement: Longer baselines give larger parallax angles and thus more precise distances. Two telescopes on different continents provide a baseline of thousands of km — ideal for NEOs at distances of 0.01–0.1 AU.
See also: NewOpenAstro/Science/Projects/radar ranging.md, NewOpenAstro/Science/Projects/Asteriod monitronig.md