Editing Light curve (section)

== {{anchor|Planetology}} Planetary astronomy ==
{{main|Planetary science}}

In [[planetary science]], a light curve can be used to derive the [[rotation period]] of a [[minor planet]], [[natural satellite|moon]], or [[comet]] nucleus. From the [[Earth]] there is often no way to resolve a small object in the [[Solar System]], even in the most powerful of [[telescope]]s, since the apparent angular size of the object is smaller than one pixel in the detector. Thus, astronomers measure the amount of light produced by an object as a function of time (the light curve). The time separation of peaks in the light curve gives an estimate of the rotational period of the object. The difference between the maximum and minimum brightnesses (the [[amplitude]] of the light curve) can be due to the shape of the object, or to bright and dark areas on its surface. For example, an asymmetrical asteroid's light curve generally has more pronounced peaks, while a more spherical object's light curve will be flatter.<ref name="lc"/> This allows astronomers to infer information about the shape and spin (but not size) of asteroids.

=== Asteroid lightcurve database ===

==== {{anchor|LCDB quality code}} Light curve quality code ====

The ''Asteroid Lightcurve Database'' (LCDB) of the Collaborative Asteroid Lightcurve Link (CALL) uses a numeric code to assess the quality of a period solution for minor planet light curves (it does not necessarily assess the actual underlying data). Its quality code parameter ''U'' ranges from 0 (incorrect) to 3 (well-defined):<ref name="LCDB"/>
* ''U'' = 0 → Result later proven incorrect
* ''U'' = 1 → Result based on fragmentary light curve(s), may be completely wrong.
* ''U'' = 2 → Result based on less than full coverage. Period may be wrong by 30 percent or ambiguous. 
* ''U'' = 3 → Secure result within the precision given. No ambiguity.
* ''U'' = n.a. → Not available. Incomplete or inconclusive result.

A trailing plus sign (+) or minus sign (−) is also used to indicate a slightly better or worse quality than the unsigned value.<ref name="LCDB" />

=== Occultation light curves ===
{{Further|Occultation#Occultations by minor planets}}
[[File:LightCurve AsteroidOccultation.png|thumb|Light curve of the asteroid [[1241 Dysona]] occulting 4UCAC 174-171272, showing instantaneous disappearance and reappearance. Duration is 6.48 seconds.]]

The [[Asteroid occultation|occultation]] light curve is often characterised as binary, where the light from the star is terminated instantaneously, remains constant for the duration, and is reinstated instantaneously. The duration is equivalent to the length of a [[Chord (astronomy)|chord]] across the occulting body.

Circumstances where the transitions are not instantaneous are;
* when either the occulting or occulted body are double, e.g. a [[double star]] or [[Binary asteroid|double asteroid]], then a step light curve is observed.
* when the occulted body is large, e.g. a star like Antares, then the transitions are gradual.
* when the occulting body has an atmosphere, e.g. the moon [[Titan (moon)|Titan]]<ref name=sicardy1990/>

The observations are typically recorded using [[video]] equipment and the disappearance and reappearance timed using a [[Global Positioning System|GPS]] disciplined Video Time Inserter (VTI).

Occultation light curves are archived at the [[VizieR]] service.<ref name=dave2016/>