Cornell University Satellite
|This article needs additional citations for verification. (November 2011)|
|Major contractors||Cornell Space Systems|
|Mission type||Technology demonstrator|
|Launch date||29 September 2013 16:00UTC|
|Launch vehicle||Falcon 9 v1.1|
|Launch site||Vandenberg Air Force Base, California, United States|
|Mission duration||6 months|
|Mass||90 lbs (40.82 kg)|
|Regime||Low Earth Orbit|
The Cornell University Satellite (CUSat) is an nanosatellite developed by Cornell University that launched on 29 September 2013. It uses a new algorithm called Carrier-phase Differential GPS (CDGPS) to calibrate global positioning systems to an accuracy of 3 millimeters. This technology can allow multiple spacecraft to travel in close proximity.
The CUSat project began in 2005 and was the winner of the University Nanosat-4 Program which aims to educate the future aerospace workforce and develop new space technologies. As part of this program, CUSat completed environmental testing and other aspects of final I&T in the AFRL Aerospace Engineering Facility at Kirtland Air Force Base. CUSat is working with AFRL to complete the Department of Defense SERB process in preparation for a launch with the Space Test Program. The satellite launched as a secondary payload to CASSIOPE on a SpaceX Falcon 9 rocket on 29 September 2013.
The space segment was originally designed to consist of two functionally identical satellites that would launch together and separate on orbit in a target-inspector configuration. Once in orbit, CUSat would use microthrust Pulsed Plasma Thrusters (PPTs) and sub-centimeter level accurate carrier-phase differential GPS (CDGPS) to navigate the satellites to within ten meters of each other. The inspector satellite would use cameras to gather imagery of the target satellite while performing relative navigation. Target satellite imagery would be transferred to the ground segment where they would be used to reconstruct a three dimensional model for the end user.
The mission was modified after one of the segments was damaged during testing. It now consists of a single satellite with multiple antennas that transmit data to each other.
Phase One: Launch
CUSat will launch as a secondary payload on a launch vehicle. Once in orbit and in the correct attitude, CUSat will separate from the launch vehicle where it will begin Phase Two - the initialization.
Phase Two: Initialization
Once CUSat separates from the launch vehicle and enters the Initialization Phase, it will enter solar illumination where the spacecraft will power on. The spacecraft will make contact with the Mission Control Center at Cornell through one of several ground stations, beaconing its status. Next, the spacecraft will begin to assess its tumble rates, and will detumble if required. Once stabilized, CUSat will begin commissioning operations. Operators in the MCC will assess the health of most satellite subsystems. Durin this time, the top spacecraft will begin to search for surrounding GPS satellites. A Carrier-phase Differential GPS Lock is then acquired to obtain an accurate attitude solution. The spacecraft will enter Phase Three: Spacecraft Separation.
Phase Three: Spacecraft Separation
Once an attitude solution is obtained, CUSat's actuators will adjust the attitude for a proper separation.
While still in illumination, CUsat is then able to perform a low-shock separation through the use of a lightband into Top and Bottom satellites. After separation, CUSat enters Phase Four: Inspection
Phase Four: Inspection
Once both Top and Bottom satellites obtain a GPS lock, the relative distance between the two will be calculated via CDGPS. When the partner satellite enters an operational camera's field of view, the inspecting satellite will acquire images of the partner satellite. The ground will request specific images, which will be subsequently downlinked from the space segment in the next communication opportunity.
On the ground, the downlinked data will then be used to construct a 3D image of CUSat to verify the CDGPS data.
Because CUSat is an Engineering Project Team at Cornell University, it is composed of a multitude of different students with a variety of abilities and talents. Team members come from such majors as Electrical and Computer Engineering, Mechanical and Aerospace Engineering, Applied and Engineering Physics, Computer Science, Economics and Management, and even Architecture. CUSat recruits Cornell students with a good technical background and a strong commitment for work, regardless of their level.
There has been a major redistribution of work, into different subsystems since FCR. The current Subsystems are listed below.
- ADCNS:The Attitude Determination, Control, and Navigation Subsystem (ADCNS) executes the relative navigation that will be used for CUSat's in-orbit inspection procedures. CUSat will primarily be using three GPS boards for attitude determination. For attitude control, CUSat will be using pulsed-plasma thrusters (PPTs) and reaction wheels. The software portion of ADCNS will consist of the relative navigation algorithms, which will run the various modes of operation defined by the CONOPs.
- Camera: The camera team is responsible for acquiring images while in orbit, compressing them in a modified JPEG format, and relaying them to the onboard computer, C&DH.
- Command and Data Handling: C&DH is the central hub for communication and computation on the satellite. Using a commercial off the shelf (COTS) single board computer running Windows CE and C++, C&DH will execute the ADCNS algorithms and flight code.
- GPS: The GPS team is responsible for the GPS receivers, antennas and algorithms used to calculate sub-centimeter relative positioning.
- Ground Segment: The Ground Segment is responsible for the ground operations of the satellite, including ground to satellite communication, tracking and commanding.
- Harness: The Harness subsystem is responsible for satellite wiring, the electronics backplane, the electrical interface boards, and any System level electrical concerns.
- Industry Relations: The Industry Relations team is responsible for marketing CUSat and seeking commercial and academic sponsorship.
- Integration and Testing: The I&T team is responsible for enabling rapid integration and testing of CUSat. I&T is also responsible for testing CUSat in Cornell University's thermal vacuum chamber.
- Mechanical Hardware: The Mechanical Hardware team manufactures the satellite structure and manages the design. The structure includes eight isogrid panels as well as numerous electronics board enclosures.
- Mission Ops: The Mission Ops team defines the detailed, on orbit operations plan for both CUSat satellites. Operating procedures are defined to match with hardware and mission specifications and help ensure successful execution of the mission.
- Power: The power team is responsible for harnessing solar energy, storing it, and distributing it throughout the satellite.
- Propulsion: The propulsion team is responsible for CUSat's pulsed plasma thrusters (PPTs) which give each satellite three degrees of translational freedom and three degrees of rotational freedom.
- Structures: The structures team is responsible for designing, analyzing, and manufacturing the body of the satellite as well as the logistics of the internal components.
- Survivability: The Survivability team is responsible for analyzing and controlling the satellite's thermal, electrical and vibrational environment on the ground, during launch, and in orbit. Analyzed effects include ESD, atomic oxygen effects, venting and outgassing.
- Systems: The CUSat Satellite project employs Systems Engineering extensively. The Systems group is largely responsible for providing the project with direction by creating top level system requirements, creating best practices, maintaining communications, making design choices, and creating processes for creating a successful product. Each of the subsystem leads also participates as a member of the Systems group, which allows the project to maintain consistency and focus.
- Telemetry and Command: T&C is responsible for intersatellite communications as well as satellite to ground communications. T&C uses modified commercial radios operating in amateur frequency bands to transmit images taken by the satellites to the ground station.
- Friedlander, Blaine (10 September 2013). "Nanosatellite CUSat to launch from California". Cornell University. Retrieved 30 September 2013.
- Malik, Tariq (29 September 2013). "SpaceX Launches Next-Generation Private Falcon 9 Rocket on Big Test Flight". Space.com. Retrieved 30 September 2013.
- Nutt, D.W. (15 September 2013). "Cornell satellite project aims for the stars". Democrat and Chronicle. Retrieved 30 September 2013.