Lab session began with students identifying main constituents of ADCS including torque rods, sun sensors and yaw sensors. Students were involved in brief discussion before any experiments were conducted to recall concepts covered in ADCS lecture.
Students first used compass to observe magnetic fields created by torque rods. Students then ran three-stage light exposure test to observe resistance and voltage fluctuations for sun sensors and yaw sensors, respectively; these three stages were no light, medium room light, and a simulation of full sun exposure with lamp. Students next verified EyasSat's three axes coordinate system by utilizing ADCS telemetry data.
After integrating subsystems covered in previous sessions with ADCS, students were then able to control reaction wheel. Lab session concluded with students observing changes in power consumption by varying reaction wheel's rotational speed.
Matthew's Problem 3 and 4 answers
By brownmk3. I think the Eyassat uses the ADCS to position itself for optimum recharging during sun-on periods. The sun sensors act as a way to coordinate the calibration of the position so that it is able to achieve the optimum intensity of sunlight.
4. I suppose it depends on how specific the pictures need to be. Obviously if you're looking for a certain phenomenon across the world then it will require a lot more sensors and equipment (and therefore functions) than say a satellite that only looks at one patch of land forever (ie google maps). In general, I suppose a satellite would need a way to position it's camera to what needs to be captured, so you would need a flywheel or something similar. You would need sensors to make sure your camera is pointed the right way. Sun sensors alone will not cut it because the sunlight will be hitting the camera at different angles as the earth rotates around the sun. Something more sophisticated, maybe a geothermal sensor, or even a pattern recognition program for the satellites camera could be used to help in positioning. Thrusters would be good if the satellite had to move between positions.
James' Group: Elizabeth, Pamela, Philip
By ElizabethPhilip Truong's Answers to Questions 3 and 4
By philipq3) The purpose of the EyasSat’s ADCS is to determine the orientation of the satellite relative to the sun via sun sensors. To do so, the satellite will first filter out the ambient light striking its yaw sensors, so that it can better locate the direction of the sun. The satellite will then determine its location relative to the sun based on the intensity and/or angle of sun light striking each one of its sun sensors. Due to the fact that the sun sensors are on different faces of the cube, each face can act as an axis of rotation that the satellite can then use in determining its orientation relative to the sun. Determining the orientation of the satellite relative to the sun can then be use to maintain the satellites orientation relative to something else if you know the location of the sun. This could be helpful when trying to take photographs, when trying to maintain a direct connection to something at all times, when trying to maximize the amount of solar energy intake, etc.
Wei-hann's Group: Dana
By danarose3) The purpose of the EyasSat’s ADCS is autonomously and continuously orient the satellite, using data from sun and yaw sensors, into a position that maximizes solar benefits. In space, solar energy is an extremely important asset to the satellites power system. If a radio antenna were out of line with a ground station, ADCS could also be used to correct this.
4) If the EyasSat’s mission were to perform geospatial imaging, which involves photographing the earth, a system requirement would be to have the camera facing the earth. We could use a combination of sun sensors, gyroscopes, horizon sensors, and magnetometers in conjunction with reaction wheels and torque rods to properly align the camera in the appropriate direction of the area that is to be studied. Once the ADCS had done its’ job, the function of the camera is to capture the image, an antenna would transmit this data to earth, all powered by an adequate power system.
Wei-hann's Group: Dana and John
By danaroseQuestion 1: According to data gathered in the lab regarding the sun sensors and given three different colored lamps, a red, blue, and yellow lamp, which would cause the greatest and least resistance and why? Does this agree with the stated behavior of a sun sensor?
Answer: Recalling recorded resistances of the sun sensors for variant light, we conclude that as the amount of energy observed by the sun sensors increases, resistance decreases. Amongst red, blue, and yellow lights, blue would have the least resistance, red would have the most resistance, and yellow would fall between the two. The reason being that in the color spectrum, ROYGBIV (which is an acronym for the relationship between the colors of light listed from least frequency to highest: red, orange, yellow, green, blue, indigo, and violet) red has the lowest frequency and blue has a higher frequency than both red and yellow light, and a higher frequency corresponds to higher energy. Yes, our answer agrees with the theoretical relation between the sun sensors and its corresponding resistance because while testing the sensor under conditions of simulated sunlight the data resembled least resistance compared to the tests of ambient light, and no light (covered sensor), which had the highest resistance.
Question 2: According to data gathered in the lab regarding the yaw sensors and given three different colored lamps, a red, blue, and yellow lamp, which would cause the yaw sensors to sense the highest voltage and why? Does this agree with the stated behavior of a yaw sensor?
Answer: Recalling recorded voltages of the yaw sensors for variant light, we conclude that as the amount of energy observed by the sensors increases, voltage increases. Amongst red, blue, and yellow lights, blue would have the greatest voltage, red would have the least voltage, and yellow would fall between the two. The reason being that in the color spectrum, ROYGBIV (similarly stated in previous response) red has the lowest frequency and blue has a higher frequency than both red and yellow light, and a higher frequency corresponds to higher energy. Yes, our answer agrees with the theoretical relation between the yaw sensors and its corresponding voltage because while testing the sensor under conditions of simulated sunlight the data resembled greatest voltage compared to the tests of ambient light, and no light (covered sensor), which had the least voltage.
Alex Gao's Answers to 3 & 4
By Alex Gao3) The purpose of the EyasSat’s ADCS is to process data from strategically placed sensors and act on the data it receives in order to orient the EyasSat in a position which would allow its solar cells to receive the most amount of light from the sun for a better supply of power. The ADCS could also manually be controlled with the software for any instances where direct control may be necessary.
4) The ADCS should be able to communicate with other equipment, such as the camera, in order to process any data the camera might provide. The ADCS can then make necessary adjustments to, for example, keep the camera as still over a location as possible. The ADCS would also need sun and yaw sensors to allow the satellite to absorb the most amount of solar power possible, which will eventually help power the equipment needed for geospatial imaging. The ADCS should be capable of making movements in all 3 dimensions (pitch, roll, yaw) in order to orient the camera and other equipment into the required positions. The ADCS should also be able to follow automated commands such as those needed to position the satellite to take a panoramic photo.
John's Group's Answers to 1 & 2
By Alex GaoJohn's Group: Matthew, Alex
Question 1: According to data gathered in the lab regarding the sun sensors and given three different colored lamps, a red, blue, and yellow lamp, which would cause the greatest and least resistance and why? Does this agree with the stated behavior of a sun sensor?
1)The yellow light would have the least resistance because the sensor under full light had the least resistance. The full light was “white light,” which is created by combining red, green, and blue light. Yellow is a combination of red and green, and thus should be closer to white light than either red or blue. The sensor under no light conditions had the most resistance, so either the red or blue light should have the greatest resistance. This agrees with the theoretical relationship that the sun sensor’s resistance drops under illumination.
Question 2: According to data gathered in the lab regarding the yaw sensors and given three different colored lamps, a red, blue, and yellow lamp, which would cause the yaw sensors to sense the highest voltage and why? Does this agree with the stated behavior of a yaw sensor?
2)The sensor under no light had the least voltage, so the sensors under either the red or blue lights should also have the least voltage (see question 1). Yellow light, being a combination of red and green, should have the greatest voltage because the sensor under full light had the greatest voltage. This agrees with the theory that full light causes the highest voltage, while no light causes the least voltage (ambient light is in between these two). The yaw sensors would help guide the satellite to face the direction in which it senses the greatest voltage.
Wei-Hann's Group: John
By jfurumoProblem 3)
The purpose of the EyasSat’s ADCS is determine the attitude or orientation of the spacecraft and then make the necessary control maneuvers to maintain a proper attitude and orbit. The ADCS achieves this by using sun sensors to determine its orientation relative to the sun. Using this information, torque rods and a reaction wheel create magnetic and mechanical torques that act to align the spacecraft with the Earth’s magnetic field. The ADCS is a vital subsystem to the spacecraft’s mission, as the Communications subsystem and most payloads are attitude sensitive.
Problem 4)
Attitude Determination and Control is a very important subsystem to a satellite designed for a geospatial imaging mission. This task involves photographing or filming the earth from orbit. In order to do this, the onboard camera or scanning apparatus must be directed at the portion of the earth’s surface that is of interest. This requires a precise attitude at all times during orbit. Such a satellite would need to make use of sensors such as sun sensors, gyroscopes, horizon sensors, or magnetometers that would accurately determine the orientation of the satellite in space. Actuators such as reaction wheels and torque rods or thrusters for larger satellites would then make the necessary adjustments to the attitude of the satellite. These would need to very precise, as it takes a steady hand to take a good picture, so to speak.
Pamela Toshi's answers to questions 3 & 4
By ptoshi3) The purpose of the ADCS is to determine the positioning of the satellite. It uses the sun sensors to determine the direction it's facing; direct light means it's facing the sun, ambient light means its facing the earth, and no light means it's facing out towards space. This way, the satellite will know if it needs to reposition itself.
4) If the satellite is performing geospatial imaging, it will need to constantly face the earth. Therefore, it will need sun sensors to determine the direction it's facing, a way to keep it pointing towards the earth (like gravity gradient stabilization), and a way to adjust its positioning if it's not facing the right way (like thrusters).
Elizabeth Viernes' Critical Thinking Response
By Elizabeth3) In the lab, the satellite uses sun sensors and we were testing the different types of light that it might encounter. Since we performed these experiments, I think that the purpose of the EyaSat's ADCS to to orient the satellite so that one side would face the sun and gather solar energy to recharge the power of the satellite. While having one side facing the sun, the other side can relay information to the ground station or gather data. The sensitivity of the sun sensors allow the satellite to see if it is facing the sun (full light), the Earth (ambient light), or outer space (no light).
4) For the EyaSat to perform geospatial imaging, the ADCS would require having one side of the satellite always pointing towards Earth. In order to achieve this task, we can use gravity gradients or magnetic torque rods to use the Earth's gravity or magnetic field to orient the satellite to face the Earth. We could also use sun sensors so that the satellite knows which side is facing the sun and it can communicate to the ADCS to point the satellite in the correct direction.