Apparent brightness series#

This synthetic light curve model was applied to a wide range of simulated and real-world light curve examples. The selected approach was to develop a synthetic light curve generation model which was then used to improve understanding of optical light curve data. The aim of this PhD research was to develop novel methods to derive information on space objects from their light curves, and so augment present day SSA capabilities. This has been performed extensively in the literature for natural objects such as asteroids, and has also been applied to artificial space objects such as active or inactive spacecraft and rocket bodies.

Apparent brightness series#

In this context, a light curve is a high cadence series of brightness measurements, typically in the visual band on the order of a few minutes in duration. It is therefore possible to determine information about a space object’s attitude state by inverting light curve data. The brightness of an object is, in part, a function of its orientation with respect to the source of illumination and the observer. One important area of interest for exploiting optical installations is to understand the relationship between a space object’s brightness and its attitude state. For this reason, there is considerable interest in the global SSA community to maximise the potential of optical installations. Optical telescopes can be built and operated at substantially reduced cost and therefore present an attractive alternative. However, these radar installations are extremely costly to build and operate. Radar installations are invaluable for observing space objects as they can operate 24-hours per day regardless of weather and, in the cases of phased array radars, can observe large numbers of objects simultaneously. The large and increasing number of objects in Earth orbit has motivated improvements to the global Space Situational Awareness (SSA) capability. Because light becomes dimmer the farther the viewer is from its source according to the inverse-square relation, we can figure out how far away the galaxy is, and roughly how far away all the other galaxies in its cluster are, simply by measuring how bright it appears to us.This PhD thesis focuses on the relationship between space object attitude state and time-varying brightness signals. Therefore, by looking at a galaxy and determining its type, we know its luminosity. Since a galaxy's 'type' is based upon simpleĬues, it is possible to tell what type a galaxy is just by looking at it, almost as if light bulbs of different wattages were different shapes. The galaxy is at the source, or in a sense the 'wattage' of the Same intrinsic brightness (luminosity), which is a measure of how bright This is why the streetlight does not hurt your eyes from far away, but does from a small distance.Īstronomers have discovered that galaxies of a certain type have the In other words, as you move away from a light-emitting source, the more quickly it appears to grow dim. This relationship means that the brightness of an object to an observer (apparent brightness) is equal to the amount of light the object emits per second (luminosity) divided by the distance the observer is from the source squared (distance 2) times a constant number (4 ). Which is called the 'inverse-square relation.' This is because light is related to distance in the following way: However, if you looked at that same streetlight close up, it would hurt your eyes. Think of streetlights on dark nights: from far away it is possible to look at a street light with no discomfort.

Red shift, but is much simpler to carry out is Galactic Distanceīrightness is a good measure for astronomers to use because of the simple way it relates to distance.

One common measurement for distance that does not reach as far as It is useful to have many methods available to make the measurements they They are encouraged to be as efficient as possible and therefore Astronomers areįrequently hindered by the limits of observation time and availableįunds. Is useful to make more simple measurements that have smaller limits toĭetermine distances to objects which are closer. Today and can reach beyond 100 million parsecs. Relation is one of the farthest reaching measurement strategies known Types of measures is that each of these measurements suffer limitationsĪnd are only accurate for objects within a certain distance from Earth.

Another important reason for creating different For this reason,Īstronomers have developed many different ways to measure distance toĪstronomical objects. That results can be compared to ensure accuracy. Because astronomers make so many measurements that are indirect, it isīeneficial to have many different ways of measuring the same thing so