Nanosatellites: more than an educational tool?

Space, hitherto an area restric­ted to a few gov­ern­ment­al agen­cies, is now access­ible to a wide range of people. As such, satel­lites have benefited from the mini­atur­isa­tion of elec­tron­ics to shrink to the size of “nanosatel­lites”. Even if this cat­egory is not clearly defined, it gen­er­ally des­ig­nates small-sized satel­lites: between 1 and 25 kg, while “min­isatel­lites” weigh between 100 and 500 kg and a stand­ard tele­com­mu­nic­a­tions satel­lite weighs nearly 6,000 kg.

Their small size, low cost and the rise of an eco­sys­tem of sup­pli­ers have gran­ted stu­dents, sci­ent­ists, or private com­pan­ies, an easi­er access to space. From 1998 to 2012, only 136 nanosatel­lites were launched. In the past sev­en years, this fig­ure has been mul­ti­plied by 10 and has reached a total of 1338 nanosatel­lites. They have a bright future ahead of them: an estim­ated 630 nanosatel­lites are to be launched on aver­age each year in the near future¹.

The ori­gins of nanosatellites

Intro­duced as a design exer­cise at the Stan­ford Uni­ver­sity in 1999, the Cube­Sat format is one of the pre­curs­ors of nanosatel­lites. It is the first stand­ard space plat­form which made it pos­sible to reuse sys­tems between dif­fer­ent mis­sions. It allowed many com­pan­ies to offer ele­ments based on the plug-and-play mod­el to rap­idly devel­op new mis­sions. In view of the pro­lif­er­a­tion of these satel­lites, ride­share launch ser­vices (to allow com­pan­ies to share launch­ers) became wide­spread and many launch pro­jects emerged. More than 140 micro-launch­ers are now in devel­op­ment to meet the increas­ing demand and eight of them are already oper­a­tion­al².

Sci­ent­ists and engin­eers very quickly used these new low-cost plat­forms to devel­op mis­sions of tech­no­logy demon­stra­tion, like the GomX series (ESA and Gom­Space), as well as sci­entif­ic mis­sions like AMIC­al Sat, UVSQSat and Eye­sat to only men­tion French Cube­Sats launched in the past two years.

Their small size does not pre­clude com­mer­cial mis­sions. This has not gone unnoticed by French com­pan­ies which have sent into orbit satel­lites such as ANGELS to loc­ate beacons (Hemeria, 2019), or the BRO satel­lites for elec­tro­mag­net­ic intel­li­gence (Unseen­Labs, 2019 and 2020).

A power­ful edu­ca­tion­al tool

Their reduced cost usu­ally makes nanosatel­lites a first-class edu­ca­tion­al tool. They answer a real need in high­er edu­ca­tion by mak­ing it pos­sible for stu­dents to acquire con­crete exper­i­ence through stu­dent pro­jects. Indeed, up until now, an engin­eer left his or her school with a won­der­ful the­or­et­ic­al back­ground, but with no prac­tic­al exper­i­ence. This prob­lem is even more import­ant in the space sec­tor because engin­eers, once they get a pos­i­tion, can spend years design­ing a space sys­tem without ever really see­ing it.

Par­ti­cip­at­ing in a space pro­ject dur­ing stud­ies thus rep­res­ents a rich exper­i­ence for stu­dents. All the more so since they work on vari­ous fields cov­er­ing mech­an­ic­al design and embarked data pro­cessing, as well as thermal ana­lys­is and flight mech­an­ics, not to men­tion pro­ject man­age­ment and team­work. The exper­i­ence is all the more reward­ing because a nanosatel­lite remains a com­pletely non-repair­able autonom­ous sys­tem oper­at­ing in a dif­fi­cult, even hos­tile, envir­on­ment: there is no second chance.

It is for these reas­ons that the École Poly­tech­nique chose to ment­or Cube­Sat stu­dent pro­jects as early as 2011. The X‑CubeSat mis­sion (mem­ber of the QB-50 mis­sion launched in April 2017, and which ended in Feb­ru­ary 2019) involved more than 80 stu­dents from 7 dif­fer­ent year groups. Fol­low­ing that oper­a­tion­al and aca­dem­ic suc­cess, a second pro­ject, named Ion­Sat³, was ini­ti­ated by the Space Centre of the École Poly­tech­nique in 2017, in col­lab­or­a­tion with the Thrust­Me start-up. The main mis­sion of Ion­Sat is keep­ing the nanosatel­lite in very low orbit thanks to an elec­tric thruster. More than 50 stu­dents have already con­trib­uted to the pre­lim­in­ary design of this 6‑unit Cube­Sat (a volume of 30x20x10 cm). But these pro­jects are also of interest for major stake­hold­ers. Thus, Ion­Sat is led in part­ner­ship with Thales Alenia Space, which is, in addi­tion to ArianeGroup, a spon­sor of the edu­ca­tion pro­gram “Space: sci­ence and space-related chal­lenges” of École polytechnique.

The new paradigm of constellations

The lim­ited per­form­ance of these nanosatel­lites is off­set by their use as satel­lite con­stel­la­tions (mean­ing in net­works or swarms) in order to offer ser­vices which typ­ic­al mis­sions can­not achieve. The Amer­ic­an com­pany Plan­et thus launched more than 100 3‑unit Cube­Sats (30x10x10 cm) between 2013 and 2020 to observe all the Earth’s sur­face at least once a day. In 2020, 90 con­stel­la­tion pro­jects were thus recor­ded⁴.

How­ever, all the weak­nesses of nanosatel­lites can­not be solved by launch­ing them in great num­bers. For example, there is a ques­tion of bal­ance between the part of the satel­lite ded­ic­ated to the mis­sion and the oth­er func­tion­al­it­ies, for instance to main­tain orbit. For obser­va­tion, res­ol­u­tion is pro­por­tion­al to sensor size, nanosatel­lites are thus lim­ited in this respect. The format poses fur­ther lim­it­a­tions, espe­cially with regard to com­mu­nic­a­tions: these are lim­ited by the low agil­ity and elec­tric­al capa­city of the platform.

To face these chal­lenges, some com­pan­ies, like the Kineis com­pany from Toulouse, pro­duce slightly big­ger satel­lites, but which are still small enough to belong to the “nanosatel­lite” cat­egory. Oth­ers, with a big­ger mar­ket, have chosen to increase the per­form­ance of their satel­lites by tak­ing advant­age of the bene­fits of con­stel­la­tion without lim­it­ing their size to the nanosatel­lite format. That is why more ambi­tious mega-con­stel­la­tion pro­jects, such as OneWeb and Starlink, focus on “Small­Sats” (150 kg and 230 kg, respect­ively). With a big num­ber of low-cost but power­ful satel­lites, they have the best of both worlds.

A strong lat­ent potential

Yet nanosatel­lites will not stay lim­ited to low-cost or edu­ca­tion­al pro­jects only. Indeed, the exper­i­ence feed­back from pion­eer mis­sions has shown their value in the con­text of sci­entif­ic mis­sions⁵. In addi­tion to observing Earth, as pre­vi­ously men­tioned, these Cube­Sats can be used in sol­ar weath­er research thanks to mass spec­tro­met­ers (SENSE in 2013) or X‑ray detect­ors (MinXSS in 2016); in astro­phys­ics with the mini­ature tele­scope ASTERIA (2017) or the HaloSat mis­sion (2018); in space explor­a­tion, as was the case for the MarCO Cube­Sats (Mars Cube One) which accom­pan­ied the Insight Probe to Mars in 2018, and the Lun­ar Flash­light which will accom­pany the Artemis I mis­sion on the Moon in 2021. The applic­a­tions of nanosatel­lites are thus lim­ited only by our imagination!