MCLAREN: Miniaturised Cold Atom Gravimeter for Space Applications

The overall aim of the present project will be to develop a compact gravimeter demonstrator, test the gravimeters compact
subsystems for space compatibility and establish a development roadmap for space deployment. During the project critical
subsystems will be designed and developed that will address SWaP requirements either during the project, or provide a
clear path to their attainment.
Addressing the limitations of current cold atom sensor designs will not only identify a route to space readiness but
overcome barriers to adoption in the more immediate terrestrial gravimetry markets, and in general identify a route to make
the commercial ambitions of cold atom sensors realisable. This project will output compact and space compatible
subsystems that can form early revenue streams including space compatible drive electronics, signal generators,
miniaturised vacuum systems, fibre networks, optical architectures and wavemeters.
From the specific viewpoint of the University of St Andrews, our part of this project is to exploit the interference of light for a
key aspect of the proposal. The interference of light is an ubiquitous phenomenon due to its wave nature. In particular, light
propagating in a disordered medium undergoes repeated scattering and interference, creating a "grainy" pattern known as
speckle. This is regarded as a randomization process which destroys information contained within the initial beam and is
deleterious to many optical systems. Indeed many engineers study speckle to remove its effect. Intriguingly however there
is recently growing recognition - including key observations by St Andrews - that this complex pattern is rich in useful
information on both the incident laser source and the environment, with startling potential uses. The aim of the St Andrews
team is to use laser speckle and apply it to new forms of measurement and analysis that would benefit the gravimeter

We aim to demonstrate that the speckle patterns can be used to determine the wavelength of the light source. The
advantages of using such speckle patterns are that they are complex, and can therefore embody information in a very
small footprint, offering a departure which can supersede traditional methods for wavelength determination which use one
dimensional gratings and principles of dispersion. Furthermore, this scheme obviates the need for gas cells by using these
speckle patterns to feedback electronically to control and stabilise the output of a laser system. We would stress that very
low noise and locked laser systems are essential to operate and enable numerous cold atom technologies. In particular for
a gravimeter, locking the cooling and Raman lasers at subfemtometer resolution will yield significant advances in accuracy.
Coupling this with a system that is suited to ruggedisation and compactness for space based applications makes all-fibre
speckle based locking methods ideal subsystems for space based applications, and represents a step change for the field.

Development of a miniaturised gravimeter will lead to revenues of £12m in 5 years of which 90% will be exports. With 80%
of equipment sourced in the UK, the new production channels will deliver major economic benefits to the local supply chain
of around £9.6m.
MSL expects new positions for 7 engineers, 2 technicians and 1 admin support within 5 years of project end. Additionally,
MSL will host 2 Physics PhD secondments to develop this new technology. ColdQuanta expect their UK office will hire 4
new engineers to test and integrate systems. CQ sources 50% of their components from UK supply chains, and sales of
their subsystems will feed the local UK economy.
MSL plays a vital role as manufacturer and integrator in a regional Scottish photonics hub including UStA and Glasgow
University, by commercialising university generated ideas into novel products and delivering a return of investment to these
stakeholders. Furthermore, the UK photonics industry, that this project enhances, is an important segment of British
industry: UK photonics exports 75-95% of its output relative to UK manufacturing average of only 34%, are the 4th largest
by value of any UK manufacturing sector and produces £10.5bn of output, with a CAGR of 8%, from 15000 firms. It is
already a significant international supplier and innovator of photonics solutions with unique strengths operating in a distinct
business environment. This project will enable a British company to be a leading supplier of numerous photonic-based
products, a market segment that is expected to see significant growth beyond national downturns.
Specifically turning to the speckle based wavemeter and stabilisation work at St Andrews, this will lead to new forms of
'disruptive' thinking in the field from an academic and commercial standpoint. The avoidance of gas cells, exceptional
resolution and footprint of the device can lead to new ways of thinking of creating measurement tools. In itself our speckle
based system can open up new avenues of precision metrology measurements and lead to novel applications for ultracompact
precious wavemeters, spectroscopy use and ultimately new markets in these areas for MSL.