Guide-Star Photon Return
Estimate sodium guide-star photon return with a caller-supplied effective cross section.
Description
Guide-star return budgeting scales launched photons by a supplied round-trip transmission and effective collection factor.
Guide-star return budgeting scales launched photons by a supplied round-trip transmission and effective collection factor. Cross section absorbs upstream sodium-interaction assumptions.1
Estimate sodium guide-star photon return with a caller-supplied effective cross section.
When to use Guide-Star Photon Return
Use this tool to estimate sodium guide-star photon return with a caller-supplied effective cross section.
Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
How to use Guide-Star Photon Return and understand its results
- Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
- Enter launchedPhotons, roundTripTransmission, effectiveCrossSectionM2, receiverAreaM2, rangeMeters using the field table and calculation rules, then run the tool.
- Read geometricCollectionFraction, returnedPhotons. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| launchedPhotons | Launched photons | number; minimum: 0 | Required |
| roundTripTransmission | Round-trip transmission | number; minimum: 0; maximum: 1 | Required |
| effectiveCrossSectionM2 | Effective sodium cross section (m²) | number; minimum: 0 | Required |
| receiverAreaM2 | Receiver area (m²) | number; minimum: 0 | Required |
| rangeMeters | Guide-star range (m) | number; minimum: 0 | Required |
Enter nonnegative photon count/areas, transmission 0–1 and positive range. Return geometric collection fraction and expected returned photons.
collection=crossSection×receiverArea/(4πrange²); returned=launched×transmission×collection Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| geometricCollectionFraction | Geometric collection fraction | number; minimum: 0 |
| returnedPhotons | Expected returned photons | number; minimum: 0 |
{
"input": {
"launchedPhotons": 1256.6370614359173,
"roundTripTransmission": 0.5,
"effectiveCrossSectionM2": 1,
"receiverAreaM2": 1,
"rangeMeters": 10
},
"output": {
"geometricCollectionFraction": 0.0007957747154594767,
"returnedPhotons": 0.5
}
}Limitations and assumptions
The dimensional effective-cross-section convention must match this implementation. Collection is not capped at one; sodium density, saturation and detector efficiency are not derived.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Lidar Photon Return: Estimate monostatic lidar received photons from pulse energy and geometric spreading. For a complementary task, use MCAO Field Coverage: Estimate MCAO corrected area and science-field coverage.
References
-
Guide-Star Photon Return — tool.io
Similar or alternative tools
- Lidar Photon Return
Estimate monostatic lidar received photons from pulse energy and geometric spreading.
- MCAO Field Coverage
Estimate MCAO corrected area and science-field coverage.