ChargerSat-1 is UAHuntsville's first CubeSat and is entirely designed, built, and tested by students. The satellite is a technology demonstration of a satellite bus capable of supporting future scientific experiments. ChargerSat-1 will demonstrate three key technologies. A gravity gradient stabilization system will passively orient the spacecraft along the nadir axis. Four deployable solar panels will nearly double the power input to the spacecraft. They will also shape the gain pattern of a nadir-facing monopole antenna, allowing horizon to horizon communications.
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ChargerSat-1 is a fully operational, orbital satellite. It is a 1 kg, 10 cm cube conforming to the CalPoly CubeSat standard. ChargerSat-1 is meant to demonstrate the full capabilities of all systems needed for satellite operations. The program involves members from more than seven UAHuntsville departments exercising their skills in developing a satellite, ground station, and testing program.
The ChargerSat-1 team applied to the third call for proposals of the CubeSat Launch Initiative (CLI) in Fall 2011. Acceptance to the CLI was announced in February 2012. In November 2012, the team was consulted for launch readiness. The satellite was manifested for launch on the US Air Force's Operationally Responsive Space 3 mission. Launch occurred on November 19.
Mission objectives for the satellite:
- Improve communications for pico-satellite operations
- Demonstrate passive nadir axis stabilization for pico-satellite attitude control
- Improve solar power collection for pico-satellite operations
Goals for the overall program:
- Design, fabricate, and operate a satellite, using the capacities of a multi-disciplinary team to develop a single, integrated orbital system. The team looks to inspire and engage the public in its mission and technical concepts.
ChargerSat 1.2 is the primary flight unit and is currently in orbit! This unit was assembled in the SHC clean room and passed all required testing before its voyage to orbit.
ChargerSat 1.1 is the development unit, which was also assembled in the SHC clean room, and is identical to the primary flight unit. It is used for risk reduction, undergoing the same heavy testing required of the primary flight unit. It will be stored as a flight-ready unit, if needed.
ChargerSat 1.0 is the prototype unit. This unit was assembled and flew as a microgravity experiment in August 2012 through NASA's Flight Opportunities Program. There have been several changes to the final design since this prototype. The prototype is actively used for public demonstrations.
For more information on ChargerSat-1, check out these presentations:
- Matt Rodencal and Eric Becnel, 2012, VBS
CHARGERSAT-1 PROTOTYPE DEVELOPMENT Poster
Background - Close Up in Orbit
ChargerSat-1.2 is in orbit. In preparation for launch, the following major milestones were met:
- May 2010 - Project conception
- Fall 2011 - Proposed for NASA CubeSat Launch Initiative
- Spring 2012 - Proposed for Flight Opportunities Program
- Summer 2012 - ChargerSat-1.0 is completed
- Summer 2012 - Parabolic Flight Campaign
- Fall 2012 - Launch Manifest for orbital launch
- Spring 2013 - Flight unit assembly started
- March 11, 2013 - First vibe test
- August 4, 2013 - Day In The Life Test (Successfully Completed)
- August 5, 2013 - Random Vibration Test (Successfully Completed)
- August 8, 2013 - Bake-out Test in the Thermal Vacuum Chamber (Successfully Completed)
- August 26, 2013 - Delta Mission Readiness Review (Successfully Completed)
- September 18, 2013 - Integration (Successfully Completed)
- November 19, 2013 - from Wallops Island, Virginia (Successfully Completed)
ChargerSat-1.2: Flight Unit
The ChargerSat-1 mechanical design is a completely unique design. It was machined at UAHuntsville by students in the Engineering Prototype and Design Facility.
Three of the four deployables on ChargerSat-1
ChargerSat-1 features four unique deployable systems, three of which are seen in the above photos. On the left is the deployable dipole antenna: the primary communications system for ChargerSat-1. In the middle is the gravity gradient boom. Once deployed, the gravity gradient boom will passively stabilize the satellite along the nadir vector. On the right are the deployable solar panels. These will not only nearly double the power input to the spacecraft, but also help shape the gain pattern of the final deployable: the nadir facing monopole antenna.
The Gravity Gradient Boom is the largest deployable of ChargerSat-1. A simple and reliable design
is required for this to function properly. This video is a concept test of the GG boom.
The full length is 2 m.
The Command & Data Handling system of ChargerSat-1 is powered by Atmel's ATxmega128A1U microcontroller and programmed in C using the Atmel Studio 6 IDE. ChargerSat-1 runs a custom-built real-time operating system capable of dynamically scheduling and performing all mission operations autonomously with no intervention from a ground station. The system makes use of 8 KB of SRAM, provided on the main MCU, as well as 16 MB of external non-volatile storage, and is comprised of 21,700 lines of code across 152 files.
For more information on the ChargerSat-1 C&DH, check out these presentations:
ChargerSat-1's Electrical Power System is one of the most important systems on the satellite. It is responsible for collecting solar energy and making use of it in the most efficient manner possible, so as to maximize battery charging capabilities and satellite uptime. Students at UAHuntsville have been developing the EPS since the start of the project in 2011, and the system has gone through 3 major revisions throughout the course of the satellite's development.
Block Diagram of the ChargerSat-1 EPS
The EPS is made up of hundreds of parts and spans 15 circuit boards. The ChargerSat-1 EPS consists of:
- Nine solar panels consisting of 181 TASC Solar Cells
- Nine peak power point trackers
- Power management system
- Two battery protection circuits
- Two 2000 mAh Li-polymer batteries
- Four high-efficiency DC-DC converters
For more information on ChargerSat-1's Power System, check out these publications:
- Matt Rodencal, 2012, International Astronautical Congress
MAXIMIZING OVERALL ELECTRICAL POWER SYSTEM EFFICIENCY IN PICO/NANO-SATELLITES WITH INNOVATIVE PLUG-AND-PLAY BATTERY CHARGING SYSTEM
Abstract Manuscript Presentation
- Matt Rodencal, 2012, CubeSat Developer's Workshop
INNOVATIVE PLUG-AND-PLAY BATTERY CHARGING SYSTEM TO MAXIMIZE OVERALL ELECTRICAL POWER SYSTEM EFFICIENCY IN 1U AND 2U CUBESATS
- Matt Rodencal, 2011, CubeSat Developer's Workshop
AN AFFORDABLE, EFFICIENT, 1U CUBESAT ELECTRICAL POWER SYSTEM SCALABLE FOR 2U AND 3U SYSTEMS
ChargerSat-1 has two 70cm band radio transceivers: one connected to a dipole antenna and the other to a monopole antenna. Both transceivers will be operating at 437.405MHz. ChargerSat-1 transmits GFSK packets at 9600 baud using the G3RUH standard.
ChargerSat-1 is designed to passively stabilize using its gravity gradient boom. As a result, all the satellite needs to know is whether it stabilizes along the nadir or zenith axis. It will use an IR temperature sensor to do so. The temperature of Earth (-20 C°) is much higher than the temperature of deep space (-100 C°), so by measuring the infrared signature in the direction which the satellite is "pointing", it will be able to determine its orientation with respect to the nadir vector. If the satellite stabilizes along the zenith vector rather than the nadir, ChargerSat-1 will reorient itself by activating a single reaction control wheel.
ChargerSat-1 has a variety of sensors. While most of these are not necessary to complete the primary mission, testing these sensor systems on ChargerSat-1 will allow future ChargerSats to benefit from flight proven systems. ChargerSat-1 has the following sensor systems on-board:
- IR temperature sensor
- 3-axis MEMS accelerometer
- 3-axis MEMS gyro
- 3-axis magnetometer
- Two 1.3 Mpx camera modules (one pointed out the side of the spacecraft, the other pointed at the satellite from the tip of the gravity gradient boom)
It takes a lot of testing to put a satellite in orbit! Here are a few tests that the ChargerSat-1 team ran to make sure ChargerSat-1 will work once it gets to orbit.
- Battery Swelling
- IR Sensor BalloonSat
- Power Management System
- RF Thermal Drift
- Solar Panel
ChargerSat-1 is powered by two 2000mAh Li-Polymer "pouch cell" batteries. While pouch cell batteries are extremely lightweight, they have a down side. Unlike other types of battery packs, which have rigid hard shells protecting and isolating them from the environment, pouch cell batteries are soft and flexible. This makes them susceptible to changes in the environment. The ChargerSat-1 team was concerned that, in a vacuum, the batteries would swell and become damaged. A battery was tested in a Vacuum chamber under the following conditions:
- Uncontained (control)
- Contained in a mechanical housing (like on ChargerSat-1)
- Pressures ranging from 1atm to high vacuum
- Temperatures ranging from 25C to 40C
Battery Swell Test Setup
During the testing, the team monitored battery voltage, temperature, and displacement of the battery due to swelling. The results showed that while the uncontained battery swelled significantly, the contained battery did not. This testing proved that the ChargerSat-1 batteries will be able to survive the harsh environment of space.
The IR temperature sensor will be used on orbit to determine in which orientation the satellite stabilizes. The theory is that the temperature of earth is much higher than the temperature of deep space. To test that theory, we had to fly 2 IR temperature sensor, one pointed up and one pointed down, above the atmosphere.
Left: BalloonSat 26 leaving the ground with the IR sensor payload
Right: The IR sensor BalloonSat payload before launch
We put this payload on a high altitude weather balloon and launched it at night. The balloon popped at ~105,000ft, letting us collect data above 99% of the earth's atmosphere.
IR Sensor Data collected on BalloonSat 26
Based on data collected during the flight, we were able to prove that there is clear difference in the earth facing IR sensor and the one facing deep space. The data collected during this flight allowed us to fine tune the algorithms on ChargerSat-1
This is the satellite prototype in its microgravity test frame.
The satellite team performed a microgravity test in Houston, TX at Ellington Field. This test was used to observe and measure the forces on the satellite through each of the 5 mechanical deployments and movements.
Fullscreen Video - NonYouTube
The team is continuously practicing while waiting on the weather to clear.
The team onboard G-Force One in our experiment area.
On orbit, the power coming into the spacecraft will be anything but constant. The ChargerSat-1 Power Management System was designed to change the charging current into the batteries to compensate for this. Using a digitally controlled power supply we tested the Power Management Systems ability to track the maximum input power.
Results from the Power Management System Testing
On orbit CubeSats can experience large temperature changes over the course of an orbit. To first understand then account for thermal drift, a radio was tested to the thermal limits of the radio module. Using a heater and a block of dry ice, the frequency drift and RF power were measured from -40C to 80C though a 24 hour experiment. It was found that the radios are slightly more powerful when hot and that there was about 12kHz of frequency drift over our operating temperatures.
Frequency Drift as a Function of Temperature
For orbital operation of the radios, the temperature will not range as far. In testing, the frequency deviated under 1kHz.
As we prepared to fabricate flight units, the team heavily tested the solar panels for manufacturing defects. Working with STI Electronics, UAH RFAL, and NASA MSFC, we tested the cells for spaceflight readiness.
Thermal Shock Testing at UAH RFAL
In orbit, when ChargerSat-1 comes out of the shadow of the earth, its solar panels will be really cold, we predict as low as -45C. But they won't be cold for long. The heat from the sun will quickly bring their temperatures up. The team wanted to know if the deployable solar panels would be damaged by this sudden thermal shock. The team at RFAL tested one of our prototype solar panels in their thermal shock chamber for an entire day. Before and after the thermal shock test we took the prototype to STI to get x-ray and SEM images of the panel.
Solar panel test 1 full report - December 14, 2012
X-ray and SEM Imaging at STI Electronics
To really check the quality of the solder joints underneath the solar cells we needed to x-ray the boards. Using the digital x-ray machine at STI Electronics, we were able to examine the quality of the solder joints. With the digital x-ray images, we were able to determine that the solder joints were a high enough quality for our purposes. SEM imaging also proved useful in examining the surface of the solar cells. We found some interesting surface features that were not apparent without the SEM microscope at STI Electronics.
IV Curve Solar Flashing at MSFC
The solar panels were also tested at NASA's Marshall Space Flight Center. The Solar Simulator flashed the ChargerSat-1 solar panels with the power of the sun in less than 0.002 seconds. The IV curves generated by this testing revealed potentially devastating manufacturing issues in our solar panels. Thanks to this testing we were able to fix the issues and are that much more prepared for orbit.
Initial IV Curves of the Flight Solar Panels. The low current performance on the red line indicates that at least one of the solar cells is shorted.
ChargerSat-1 has had nearly 30 team members work on various aspects of the mission. Many of these team members have since gone to do the next step in their career. Core membership through delivery has really allowed ChargerSat-1 to reach completion.
Eric Becnel - Team Leader
Eric Becnel has been the Team Leader of the ChargerSat-1 Mission since May 2010. This date is when the concept of the mission was first written down. He has led the team through from concept to orbital operation of the satellite. He specialized in the mechanical, thermal, communications, ground station and testing subsystems in addition to supporting all other fields of development.
Matt Rodencal - Electrical Lead
Matt Rodencal has been the Electrical Lead of the ChargerSat-1 Mission since the project started in 2010. Matt has been responsible for the design, fabrication, and testing of all electrical systems on ChargerSat-1. Most of his efforts were focused on the development of the ChargerSat-1 EPS which consists of 9 power point trackers, a power management system, and a couple of DC-DC converters. He has presented this system at multiple conferences. Matt is currently the project leader of ChargerSat-2.
Mason Manning - Software Lead
Mason Manning has been a member of the ChargerSat-1 team since its conception in 2010, and the Software Lead since Fall 2012. He has designed and implemented the majority of ChargerSat-1's flight software, as well as assisted heavily in the electrical design and testing. In addition, he has worked closely with the ground station and communications engineers to ensure reliable and robust operations on orbit.
Mark Becnel - VP for BS
ChargerSat-1 Data Submission
The ChargerSat-1 team is excited to work with the community for updates on our satellite in orbit! We are able to accept your data that you have collected. Currently, all data should be sent by email. We accept images, screen shots, data files, audio files, and videos of the transmission occurring.