Size matters for satellites – big or small

In the closing decades of the 20th century satellite dishes on the ground – 'earth stations' − got smaller. The first sites were large earth stations with impressive parabolic dishes as antennas – and these still have a role to play. But the use of even very small satellite dishes to receive TV programmes brought the idea of signals from space to the general population's everyday consciousness. Now we have satellite phones and applications such as VSATs (very small aperture terminals) in a variety of applications.

But what of the satellites themselves? The reduction in size of the antennas on earth was enabled by a set of complementary technical developments which increased capabilities of the satellites in space, including that they became larger and more powerful: obviously the design of a given link depends on the situation you are designing for.

The international management of frequency use for these satellites is always evolving at World Radiocommunication Conferences (WRCs), but it is essentially a mature environment of allocations, procedures and criteria for introducing new satellite transmissions, whilst protecting existing satellite and terrestrial services on related frequencies, including passive satellite services such as earth sensing. And these procedures vary by application and by frequency band according to context.

But not all satellites are getting bigger. There is also a branch of development opening up in the other direction; so-called 'nano-' and 'pico-' satellites. This is an exciting development which raises some interesting challenges.

Nanosatellite - Image courtesy of Gomspace


At the World Radiocommunication Conference in 2012 (WRC-12), a number of CEPT countries proposed an agenda item on nanosatellites and picosatellites. WRC-12 subsequently developed Resolution 757: 'regulatory aspects of nano- and picosatellites', which called for a review of the regulatory procedures, and put the item on the provisional agenda for WRC-19. Furthermore, ITU-R study Question 254/7 called for a study of the 'characteristics and spectrum requirements of nano- and picosatellites'.

The Administrations proposing this agenda item were responding to the advent of small satellites, most notably the so-called 'CubeSats'. A CubeSat is a satellite adhering to a standard proposed back in 1999 by Bob Twiggs of Stanford University and Jordi Puig-Suari of the California Polytechnic Institute.

The CubeSat standard is based on a 10x10x10cm 1kg cube called a 'U' (for 'Unit'). The first CubeSats which were launched were mainly 1Us, but nowadays many variations exist with people exploring 6U satellites and up. But this is unprecedentedly small.

The original CubeSat 'inventors' never envisaged such a rapid adoption of their standard. Ten years after its conception hundreds of these CubeSats are being developed worldwide. Initially, universities have led this, as the CubeSats proved to be excellent hands-on educational tools, but the concept is being more and more adopted by the scientific and commercial space community. Moreover, they offer a low-entry barrier for new entrants in spaceflight activities.

A small satellite being prepared for flight - Image courtesy of Innovative Solutions in Space BV

In the early days of the CubeSats, these satellites were often regarded as amateur, educational or scientific, but nowadays, the first commercial applications have started to emerge. Commercial Earth observation, asset tracking and others are just a few of the possibilities. In fact, the timing for proposing this agenda item could not have been better, given that constellations of hundreds of these satellites could be technically ready to be launched soon.

One of the driving factors behind this growth is the fact that these satellites are – unlike their traditional counterparts – mostly based on off-the-shelf, commercial or industrial grade, electronic components. The rapid miniaturisation of these components (mainly driven by the consumer electronics industry, e.g. smartphones) allows these satellites to be small yet capable.

Back at WRC-12, the Administrations proposing the agenda item recognised that these CubeSats (after that more generally referred to as 'nanosatellites' and 'picosatellites') have characteristics which (besides their size) are different from traditional satellite systems, such as their relatively short development time, modest cost, and different form of launch arrangements. By virtue of their small size, they can be launched relatively easily as so-called 'secondary payloads', using opportunistic launch arrangements rather than dedicated launches planned long in advance. Taken together these factors constitute a major step forward.

But is the current frequency management environment suitable, given the density of use and quick timescales which may be associated with these tiny satellites? And would changes to accommodate them threaten the effective operation of the existing services on which we have come to rely? We explore these questions below.


During the current study cycle, ITU Working Party 7B (WP7B) has been working on two reports. One report, ITU-R SA.2312 'Characteristics, definitions and spectrum requirements of nanosatellites and picosatellites', as well as systems composed of such satellites, addresses study question 254/7. A second report, which is close to finalisation, addresses the invitation to ITU-R to examine the procedures for notifying space networks and to consider possible modifications.

WP7B concludes in its report ITU-R SA.2312 that the difference between traditional satellites and nanosatellites and picosatellites is becoming less distinct. In fact, WP7B concluded that, given that there are many variations of the original CubeSat concept under development, these aspects are not strictly bound to nanosatellites and picosatellites, but more broadly relevant to 'small' satellites in general. As such, a unique definition of nanosatellites and picosatellites would be outdated from the moment it was defined.

Furthermore, the studies undertaken within ITU-R have identified a number of challenges, both regulatory and non-regulatory. Some of the most notable ones are outlined below:


  1. Late knowledge of detailed orbital parameters as a result of the opportunistic launch arrangements. Furthermore, since many of these satellites are not equipped with a propulsion system their orbit will decay over mission time;
  2. The short development time of nanosatellites and picosatellites which is not in line with the usual timeline of the regulatory process according to Article 9;
  3. Limited experience with the applicable regulatory procedures by some of the Administrations involved as well as some of the developers of nanosatellites and picosatellites.


As for the third point, since many developers of small satellites are newcomers to the space arena, their Administrations are in many cases relatively uninvolved in the relevant fora such as the Space Frequency Coordination Group, or have little experience in the application of the regulatory procedures under Article 9 and 11 of the Radio Regulations. These regulatory procedures have good grounds for existence, and the past has proven that coordination is necessary. Developers are not always aware that the provisions of the Radio Regulations under Article 9 and 11 also serve to protect their rights and are not just one more regulatory obligation to fulfil.


As for the near future, it is apparent that it is becoming more important to consider the rapid growth of small satellites from a spectrum management perspective. And even though, as WP7B concluded, satellite size is not relevant from a spectrum management viewpoint, their small size has been a key factor enabling their growth and widespread adoption. Some developers and commercial operators are planning to launch as many as 100 on a single launch for a single application. A recent market study conducted by Spaceworks Enterprises Inc. provides an estimate of future numbers of small satellites launched. Furthermore, most bands currently used for satellite telemetry and control, such as the 2200-2290MHz SRS/SOS/EESS allocation, are heavily crowded and this issue offers new challenges which have not been faced before.

Now is the right time to address this growth, and make sure that an effective regulatory framework is in place in order to protect the incumbent users while at the same time enabling small satellites to be deployed and realise their potential. Studying possible allocations is not within the current scope of the provisional WRC-19 agenda item. However, the question about whether and how this growth can be accommodated within the existing regulatory framework and allocations needs to be addressed as the issue is becoming more and more relevant.

Wouter Jan Ubbels, Innovative Solutions In Space BV, CEPT coordinator for Agenda Item 9 - Issue 9.1.8

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