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Hey!
Are you enthusiastic about space and technology?
Do you like challenges and team-work?
Have you ever heard about the OSCAR project?
We are now busy with preparations of its next generation experiment, OSCAR:LITE. Our focus will be the development of a more advanced diamond based magnetometer to test during a stratospheric flight in October 2018, in the framework of the REXUS/BEXUS program organized by ESA (European Space Agency), DLR (German Aerospace Center), SNSB (Swedish National Space Board).
We are putting together a core-team of highly skilled and highly motivated students. In particular, the following positions are still open:
- Electronics responsible
- Mechanics responsible
- Software responsible
What is OSCAR:LITE?
Optical Sensors based on CARbon materials: Lightweight ITEration
LITE
- noting a product that is low in calories or low in any substance considered undesirable, as compared with a similar product
- noting a version that is comparatively less extreme, bulky, complex etc., than the previous version
- light, of little weight in proportion to bulk; of low specific gravity
What is the idea behind?
The idea is to build on top of the success of first OSCAR balloon flight and to utilize the gained experience and pass it to the next generations of students. The main goal is to promote interdisciplinarity, deepen cooperation between faculties and provide students with the unique opportunity to gain hands-on experience developing a project from the start to the end.
In the first OSCAR flight we launched an experiment focused on the degradation of organic solar cells in the stratosphere and on the construction of a prototype diamond based magnetometer with optical readout. The successful flight of the OSCAR project and the large amount of collected data served as a first confirmation that both organic-based solar cells and diamond magnetometers are suitable for aerospace applications, and suggest that further work in the field can lead to great technological advancement in the fields of energy-for-space and space-compasses. This project is going to be a successor to the diamond based magnetometer part of the OSCAR project.
With our first optical readout based prototype we revealed several limitations of this system, such as low readout speed, bulkiness, high power consumption, mechanical complexity and low long term stability caused by the optical components. Advances in field of photoelectric readout of magnetic resonance (PDMR – “the electric readout”) will allow us to fabricate a device which will overcome the aforementioned limitations, mainly reduction of mass, power consumption, complexity and will improve the sensitivity and system stability.
What are goals of this project?
Develop a miniaturized, portable and ultra sensitive diamond magnetometer based on the photoelectric readout of magnetic resonance [1]
Demonstrate that the device can function as a magnetometer for aerospace applications (3d compass, device rotation, position corrections
Verify device functions and limitations in near-space conditions for future use in cubeSat
Measure and evaluate Earth’s magnetic field at various altitudes, compare with the data from previous flight, and publish the results (noise levels, acquisition speed, performance, …)
What is it about and how it works? (little bit of science and technology)
Optical sensors based on carbon materials offer high potential for future aerospace applications. The device under test within the OSCAR:LITE experiment is a prototype diamond magnetometer with electric readout. This technology is based on carbon materials with unique electro-magneto-optical properties. The following paragraphs will discuss the physical mechanism as well as the advantages and drawbacks of this technology.
The measurement of magnetic fields is crucial in many applications ranging from navigation to data storage. Recently, it was shown that defect color centers in synthetic diamond can be employed to detect magnetic fields with sub-picotesla resolution, opening up new possibilities in areas where high precision magnetic field measurements are required, such as navigation, quantum computing, metrology and sensing.
Figure 1: (left) Nitrogen-Vacancy (NV) center in the diamond crystal lattice (right) Zeeman splitting of NV-based magnetometer
The detection is based on nitrogen-vacancy (NV) centers which are present in the diamond crystal lattice (figure 1a). NV-based magnetometers are classically based on the optical detection of magnetic resonance (ODMR). In this technique, the NV centers are illuminated by a green laser light, promoting electrons from the ground to an excited state in the NV center. The radiative decay of these electrons (to the ground state) induces the emission of red light. The photo-luminescent (optical) transitions associated with the spin sublevels of the NV ground state present different brightness. The application of a microwave field with resonant frequency drives electrons from the |0> to the |±1> spin sublevels, and leads therefore to a drop of the luminescence intensity. The presence of an external magnetic field induces a splitting between NV |±1> spin sublevels (Zeeman effect), resulting in a splitting between the microwave resonant frequencies (Figure 1b). From this effect, it is possible to determine the magnitude of the magnetic field. This optical method was demonstrated in first OSCAR flight.
In 2015, it was demonstrated by our research group that the magnetic resonance of NV-centers in diamond can be measured by probing the photocurrent instead of the optical read-out[1]. This direct photo-electric read-out of NV centers, called photocurrent detection of magnetic resonance (PDMR), is based on the detection of charge carriers promoted to the conduction band of diamond by two-photon ionization of NV centers. Minima are detected in the measured photocurrent at resonant microwave frequencies, due to the spin-dependent ionization dynamics of NV centers. This detection technique only requires the fabrication of electrodes on the diamond chip by standard lithography and avoids the complexity of optical detection, allowing further miniaturization of the magnetometer. By using this technique the diamond sensor serves as its own detector.
As these devices are based on diamond, they exhibit a very strong radiation hardness, which makes them well suited for aerospace applications. Furthermore, due to their size they have a very small footprint, they are stable in a very broad temperature range and possess a high dynamic range combined with higher sensitivity compared to commercially available magnetic sensors based on the Giant Magneto Resistance effect (GMR) or Flux-gates. Characteristics of the diamond based magnetometry device enable sensing of the magnetic field in 3 dimensions. Another advantage of this device is the capability of simultaneously measuring the magnetic field and the temperature. All these features emphasize the potential of a diamond magnetometer for aerospace applications
What is the concept of this experiment?
The concept of the experiment (see figure 2) is to allocate a PDMR magnetometer on a boom, sticking out of the gondola to minimize the influence from and to other experiments. The payload box with electronics, providing communication and data transmission between ground station and the magnetometer sensor, will be on board of the gondola.
concept.png
Figure 2: Experiment concept layout
What is a core-team and what are the responsibilities?
The main roles of core-team are:
- overview of the project
- effective distribution of task and responsibilities for task finalization
- project planning, scheduling and task execution
- resource management and overview of task progress
- problem solving
- attending reviews and events
Figure 3: Preliminary mind-map of responsibilities of each core-team member
How is it with timing and workload?
Figure 4: Time overview of critical review points in the course of the project
Gantt chart in figure 4 demonstrates the workload of the project. Green marks represent days when results of acceptance/denial of the project are received. Yellow represents standard workload and Red represents critical steps and periods of time, when the workload or severity of task(s) peaks.
For example, (2) preparation of project proposal is a very critical part for invitation to selection workshop, or (12) Integration progress review preparations are when the amount of hands-on and experiment integration is increasing, or (14) Experiment acceptance review preparations: in the first OSCAR flight this was when majority of bugs, mistakes and interferences occurred, therefore this period is marked red, also because of its severity (final review == flight ticket).
Also from past experience we concluded that the majority of peaks in workload in later stages could have been reduced by proper planning, increased focus in designing and better decisions during early stages (CDR, PDR).
What is plan in next few months?
How important is this project for future?
One of the aims of this project is to verify the viability of this device to be used in a cubeSat mission. The precision of this device combined with its small footprint can provide a perfect solution for this kind of applications. For example, in satellite missions for accurate altitude determination is essential to know how the satellite is oriented in the inertial space. To do so, low Earth orbit satellites can use a magnetometer to read the magnetic field of the Earth and compare it with a geomagnetic reference field (i.e. IGRF). For this it is necessary to know the position of the spacecraft at the exact moment (GPS, laser ranging or combined). Then, by taking the reference field in that position and comparing it with magnetometer readout, a rotational matrix can be calculated. In the next step the rotational matrix is used to determine the precise orientation of the satellite.
Do you want to join us?
Do you have a question?
Contact us!
Reference
[1] E.
Bourgeois, A. Jarmola, P. Siyushev, M. Gulka, J. Hruby, F. Jelezko, D. Budker
& M. Nesladek, Photoelectric detection of electron spin resonance of
nitrogen-vacancy centres in diamond, Nature Communications 6, 8577 (2015)
