Compact Spaceborne Magnetic Observatory (COSMO)
The Compact Spaceborne Magnetic Observatory (COSMO) is a 6U CubeSat with a simple, straightforward mission: measure the Earth’s magnetic field. Earth’s magnetic field is commonly represented via the World Magnetic Field Model (WMM). The WMM is used in a variety of realms including in your phone’s compass and for research purposes. Data for the WMM is currently taken from a mission called SWARM. The SWARM mission is to be commissioned in ~2023 and needs to be replaced. This is where COSMO comes into play. COSMO can provide WMM data at a low cost, ensuring sustainable measurement for decades to come.
COSMO may sound simple, but beneath the surface, this simple-sounding measurement is very difficult. We need to measure the magnetic field with an accuracy of one part in 100,000; we need to measure three vector components of the field, while also knowing the spacecraft orientation (attitude) to within a few arcseconds; and we need the spacecraft to be magnetically clean, i.e. it should not produce a large amount of magnetic noise. For this last reason, we need to design the CubeSat bus from the ground up, ensuring we take all precautions to avoid excess noise. In addition, the magnetic field created by each component of the bus must be characterized in order to ensure that the magnetic field data is not being corrupted by the CubeSat’s magnetic field and the measured Earth’s magnetic field is to the accuracy and precision required.
The design of COSMO began in summer 2018 and continue over the next few years. The idea comes from the Graduate Projects curriculum, ASEN 5018/6028-013. The design has changed rapidly in order to develop an efficient low cost solution to meet the given requirements. The design was a 1x6U CubeSat, but we decided to change to a 3x2U CubeSat afterwards. There is a boom that can extend our payload, magnetometer and star trackers, away from the noisy components (solar arrays, electronics, and reaction wheels). The spacecraft will be powered via solar arrays and will be designed and built in conjunction with the Laboratory of Atmospheric and Space Physics (LASP).
COSMO may sound simple, but beneath the surface, this simple-sounding measurement is very difficult. We need to measure the magnetic field with an accuracy of one part in 100,000; we need to measure three vector components of the field, while also knowing the spacecraft orientation (attitude) to within a few arcseconds; and we need the spacecraft to be magnetically clean, i.e. it should not produce a large amount of magnetic noise. For this last reason, we need to design the CubeSat bus from the ground up, ensuring we take all precautions to avoid excess noise. In addition, the magnetic field created by each component of the bus must be characterized in order to ensure that the magnetic field data is not being corrupted by the CubeSat’s magnetic field and the measured Earth’s magnetic field is to the accuracy and precision required.
The design of COSMO began in summer 2018 and continue over the next few years. The idea comes from the Graduate Projects curriculum, ASEN 5018/6028-013. The design has changed rapidly in order to develop an efficient low cost solution to meet the given requirements. The design was a 1x6U CubeSat, but we decided to change to a 3x2U CubeSat afterwards. There is a boom that can extend our payload, magnetometer and star trackers, away from the noisy components (solar arrays, electronics, and reaction wheels). The spacecraft will be powered via solar arrays and will be designed and built in conjunction with the Laboratory of Atmospheric and Space Physics (LASP).
Our Work
The LAIR is responsible for design and build the payload and the structure of COSMO, while the CubeSat bus and ground station are responsible to LASP. This payload includes the attitude determination system (i.e., star trackers) and of course the magnetometer. The magnetometer we used is a vectorized Rubidium optical magnetometer (VRuM). The design of this magnetometer is focused on minimizing volume, mass and power requirements while ensuring the accuracy and precision necessary for WMM. As the name implies, the magnetometer is consists of two Rubidium scalar magnetometers within a Braunbek coiled cube. By this design, VRuM is capable of taking scalar measurements, while adapting to take vector measurements as well. This vectorization method has never been done for Rubidium optical magnetometers to the precision and accuracy needed. Although COSMO’s magnetometer has a little heritage, and its development effort is great, this magnetometer offers several advantages over other magnetometers that have already been developed for CubeSats. Most importantly, since an optical magnetometer’s operating principle is based on the effect of magnetic fields on atomic properties, its measurements are absolute, do not vary with time, are not sensitive to changes in temperature and do not exhibit offsets that need to be calibrated for.
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Left: Coiled Braunbrek cube with two scalar Rubidium magnetometers inside. Middle: The CAD model of the Braunbrek cube (Adapted from Chism et al., 2025). Right: The inner view of the cube with two scalars.
In addition, a large effort is being made in the magnetometer development to ensure it is space qualified. In May 2025, the integrated COSMO is shipped to NASA Goddard Space Flight Center (GSFC) for conducting a series of tests in a 42 ft Braunbrek coil system. In this facility, the Earth's magnetic field can be nulled and apply arbitrary magnetic field in any magnitude and direction. Our team gathered a great amount of valuable data that can help us improve our system more accurately and precisely.
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Left: COSMO testing at the 42 ft coiled facility of GSFC. Right: The integrated view of COSMO.
All satellites and CubeSats ride-share on the Transporter-16 mission. (Image credit: Exolaunch)
COSMO is integrated at the end of October 2025, finish the environmental tests at the end of December 2025, deliver to launch service provider in the mid-February 2026, and integrated with the Falcon-9 rocket. On March 30, 2026, COSMO has been successfully launched in Space X Transporter-16 mission from the Vandenberg Space Force Base, California. After a few weeks of commissioning, COSMO can start collecting science data in orbit!
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Left: COSMO on the CubeSat dispenser. Right: COSMO being released to the space. (Image credit: SpaceX)
References
Chism, C. T., Marshall, R. A., Aguilar-Nadalini, A., Knappe, S., Malaspina, D., Hughes, K. J., Ellmeier, M., Wankmueller, S., Cunningham, C., Maydew, T., & Alem, O. (2025). Design of a vectorized rubidium scalar magnetometer for SmallSat applications. Advances in Space Research, 76(8), 4635-4646. https://doi.org/10.1016/j.asr.2025.07.011
