Difference between revisions of "Navigation Sensors"
m (fixed categories) |
(added DDM) |
||
| Line 21: | Line 21: | ||
The main disadvantage of LIDAR is that it used a fairly concentrated beam; and thus the sweep area of a LIDAR detector is extreamly small compaired to that of the radar. By combining the two, we can use the radar to scan broad areas for navigational hazard; whereas the LIDAR is used only for specific areas of interest and to study gasseous phenomina such as planetary rings and gas clouds | The main disadvantage of LIDAR is that it used a fairly concentrated beam; and thus the sweep area of a LIDAR detector is extreamly small compaired to that of the radar. By combining the two, we can use the radar to scan broad areas for navigational hazard; whereas the LIDAR is used only for specific areas of interest and to study gasseous phenomina such as planetary rings and gas clouds | ||
| + | |||
| + | ==Daily Distance Measurement== | ||
| + | |||
| + | The [[habitat]] is capable of computing it's possition within the solar system based on the theoretical speed and direction that the hab has traveled since it left earth. This, combined with the radar and LIDAR is accurate enough to ensure that the habitat does not run into any planets or moons. However, the habitat does not travel in an ideal world, and events such as solar wind and calculation errors are frequent. | ||
| + | |||
| + | To make up for these unaccounted events, we take a Daily Distance Measurement (DDM). The DDM is taken once a day, and uses the shadow that the earth casts to calculate distance. Given the orbit of the earth; the computer can predict when it's orbit will take it between the habitat and the sun; thus creating an observable shadow. The time that his shadow is observed by the sensors on the habitat is compaired with the time that the earth should have passed in front of the sun. Since it takes time for light to travel from the earth to the wherever the [[habitat]] is located, there will always be a time delay between the eclipe occuring and when the habitat detects the shadow. Thus, by measuring the time delay, we can calculate the distance traveled. | ||
Revision as of 23:02, 16 April 2006
Radar
To detect large objects such as space debris and asteroids, the habitat uses a continuous wave rader(CWR) system similar to that used on advanced air to air missiles. Each continuous wave radar system of the habitat consists of two radar dishes. One dish sends out a continuous radar signal and the other dish is devoted to recieving the signal emmited by it's counterpart. This enables the radar system to calculate the velocity of the target by calculating the frequency shift due to the doppler effect.
A continuous radar wave emmited at a certain frequency is incapable of calculating distance. To make up for this deficiency, the amplitude of the radar waves is moved up and down. When a reflection is received the amplitudes can be examined, and by knowing when in the past that particular amplitude was sent out, you can do a range calculation to determine the distance between you and the object.
LIDAR
There are several disadvantages to the CWR system on board the habitat. It is easily disrupted by radiation and pulsars, and it cannot detect gas clouds. To compensate for these deficiencies, a light based system has been installed in addition to the CWR. LIDAR, or Light Detection and Ranging, uses a reflected light beam to detect objects. It does this be emiting a light beam at a known frequency (usualy in the infrared or ultraviolet). This light is reflected by various objects and is picked up by a reciever. In addition to being able to detect gasses, the LIDAR can determine the types of gasses present; as certain gasses react in a certain way to ultraviolet and infrared light. These changes can be picked up by the LIDAR and can help determin the chemical makeup of the gas cloud.
Also, since it can detect clouds and gasses, LIDAR can be used to gather meterological data about planets.
The main disadvantage of LIDAR is that it used a fairly concentrated beam; and thus the sweep area of a LIDAR detector is extreamly small compaired to that of the radar. By combining the two, we can use the radar to scan broad areas for navigational hazard; whereas the LIDAR is used only for specific areas of interest and to study gasseous phenomina such as planetary rings and gas clouds
Daily Distance Measurement
The habitat is capable of computing it's possition within the solar system based on the theoretical speed and direction that the hab has traveled since it left earth. This, combined with the radar and LIDAR is accurate enough to ensure that the habitat does not run into any planets or moons. However, the habitat does not travel in an ideal world, and events such as solar wind and calculation errors are frequent.
To make up for these unaccounted events, we take a Daily Distance Measurement (DDM). The DDM is taken once a day, and uses the shadow that the earth casts to calculate distance. Given the orbit of the earth; the computer can predict when it's orbit will take it between the habitat and the sun; thus creating an observable shadow. The time that his shadow is observed by the sensors on the habitat is compaired with the time that the earth should have passed in front of the sun. Since it takes time for light to travel from the earth to the wherever the habitat is located, there will always be a time delay between the eclipe occuring and when the habitat detects the shadow. Thus, by measuring the time delay, we can calculate the distance traveled.
