EQUiSat

Payload

EQUiSat’s primary payload includes a radio, which will transmit messages to Earth receivable on ham radio, and a high power LED array, which when flashed will appear on Earth as bright as the North Star. The payload will be used to engage those on earth, especially in pursuit of the project’s primary mission, which is to make space more accessible to the public.

The secondary payload is the lithium iron phosphate (LiFePO
4) batteries that will power the radio and LEDs. The secondary mission of EQUiSat is to test the viability of LiFePO
4 batteries, which have never been flown in space, making the batteries more than power storage units but a payload themselves.

Mission

EQUiSat has a primary and secondary mission. The primary mission of EQUiSat is to increase the accessibility of space, especially through education. The secondary mission of the project is to test the viability of operating LiFePO
4 batteries in space. One way that Brown CubeSat Team will advance EQUiSat’s primary mission to increase the accessibility of space is by lowering the barriers of entry to similar projects. To do so, Brown CubeSat Team will maintain EQUiSat as a low-cost and rigorously documented open source project, allowing others to replicate EQUiSat’s subsystems without large budgets or extensive expertise. Brown Cubesat Team espouses a DIY philosophy to minimize costs, while also utilizing production processes that are widely achievable by and accessible to non-professionals. Brown CubeSat Team’s budget is under $13,000 and the goal is for the project to be replicated for under $3,000.

The other way in which Brown CubeSat Team will increase the accessibility of space is by educating youth on the design and role of satellites in society. Brown CubeSat Team is cooperating with schools and museums across the country to develop an educational outreach plan to teach students and the general public about the design and role of satellites in society. Upon launch, the opportunity to easily locate, hear, and see EQUiSat in the night sky provides an important tangible component to these outreach efforts.

EQUiSat’s second mission is to test the viability of operating LiFePO
4 batteries in space. A LiFePO
4 battery has never been flown in space, but it carries certain advantages over batteries of different chemistry, such as high current draw capabilities with less risk of thermal runaway than lithium-ion batteries.

Launch

EQUiSat is currently scheduled to be launched as part of ELaNa (Educational Lauch of Nanosatellites) mission 21, currently scheduled for March 2018.

Flash

The flash subsystem is an optical beacon allowing those on earth to visually track EQUiSat after launch. The beacon is an array of 10-20 Luminus SST-90 LEDs that will be flashed .2 seconds every 2 minutes when EQUiSat is in the night sky. The array will have an apparent magnitude of 2, approximately the same intensity as Polaris. In order to further increase light intensity for those on Earth, the high power LED array will all be on one panel that will be directed towards Earth’s northern hemisphere using passive attitude control and the high power LED array will be outfitted with reflectors of ~60 ̊.

Radio

A UHF transceiver onboard EQUiSat will transmit a signal in the 70 cm Amateur Radio band at 435-438 MHz, and will consist of a registered call sign beacon and sensor data. The transmissions will be receivable to amateur radio users, but will also be posted online to increase access for the general public. The radio will also act as a beacon to track the position of the satellite and will be capable of receiving uplinks from ground stations to disable transmissions.

Attitude Control

EQUiSat will use a passive magnetic attitude control system (ACS), which will require no reliance on an attitude determination system, no energy drain from torque coils or momentum wheels, and no reliance on the complex algorithms required to de-tumble and stabilize the satellite.

Electronics

The Electronics subsystem will tie together all subsystems to allow the satellite to function properly. The electronics system utilizes PIC microcontrollers to monitor the solar panels and battery states, and allow for the proper transmission of power to the microcontrollers and payloads.

Power

The power system includes solar panels for power generation in space and two battery systems for power storage.

The solar panels are designed and fabricated in-house. The panels make up 5 sides of the CubeSat, and are made up of varying configuration of Triangular Advanced Solar Cells (TASC). The cells are made of Gallium Arsenide and are 27% efficient. The top and bottom panels on EQUiSat contain 24 cells in a 4S6P configuration, and three side panels contain 20 cells in a 4S5P configuration. The panels are currently designed to output 8.76V at 140-170 mA for an average output power of just over 1.3 W in full sunlight. The configurations may fluctuate with alterations in the circuit design.

EQUiSat contains two sets of batteries: one to power the flash system and another to power the radio system and microcontrollers. The batteries that will power the flash are A123 System 18650 LiFePO4 cells in a 2S2P configuration. The batteries that will power the radio and microcontroller are 4 Lithium rechargeable coin cell batteries (LIR2450) in a 2S2P configuration. EQUiSat will alternate between battery systems, with priority going to the LIR2450 batteries first.

Structure

The chassis and other components such as reflectors are manufactured in-house. The chassis is a solid Al 6061, which provides the body of EQUiSat and fastening points for all components.