Gaia Space Telescope

As the active operations of this amazing telescope just ended last week (March 27th 2025, see https://www.esa.int/Enabling_Support/Operations/Farewell_Gaia!_Spacecraft_operations_come_to_an_end) and I couldn't find any model available online I thought what better farewell sendoff than to create a 3d printable version of this one. 

Basically, I looked for all the engineering details freely available online, sources listed at the end. Next, all the relevant sub-assemblies were put into one model each according to the exploded diagram from the main source. Models were then slightly altered to allow for snap-in fastening. The scale should be roughly 1:100. Be aware that these are very tight tolerances so, make sure your printer is dialed in. Alternatively, you could also scale the models in your slicer which I haven't printed yet myself but the results looked good in Prusa Slicer when I tested a 200% version to slice. Of course, expect some increased printing times then. If you wanted to only have the outer shell of the telescope you can skip the optional models and mounting steps but I added them for completeness. 

Ordered in the sequence of mounting, the individual models are for Subassembly 1:

1. DSA - Deployable Sunshield Assembly. Its bottom side is the one with the grooves for solar panels. To avoid supports I'd suggest to print it upside down like in the g-code provided.
2. SMMS - Service Module Main Structure - Snap into pins of DSA from below (such that the solar panel grooves face away from the SMMS. While the pins of each part should engage with each other, the SMMS will not be properly fixed yet. Also, the “front” of this part is the side with the cut off top ring. If you like to be as accurate as possible in the alignments, in the real telescope this front faces a side of the DSA that has no solar panels attached to its bottom.
   Note: to asses whether the SMMS fits properly onto the pin of the Display Stand and whether that pin might need so post-processing, it is suggested to trial their connection at this point before the entire telescope model has been assembled.
3. SPA - (8) Solar Panels Array - Align solar panels according to grooves of DSA and snap in from the bottom. Turn the assembly around to make sure that the SMMS and the DSA are still properly engaged. By now you should be able to snap in the SPA from below such that its protruding top ring sits right between the inner side walls of the DSA and the outer sides of the SMMS. Make sure you press onto each of the solar panels to properly snap each of them into the designated groove on the DSA as this will greatly increase stability of the entire bottom assembly.
4. FSA - Fixed Solar Array - Align the grooves of its top-side ring to the pins of the SPA and snap into place from below.
5. (Optional) ASP - Antenna Support Panel - Align its outer grooves to the elevated cylinders on the inside bottom of the SMMS and snap in place from the top. Can alternatively already be put into place before merging the SMMS with the DSA.
6. (Optional) PPTA - Propellant and Pressurant Tanks Assembly - Take the ring above the top of the SMMS and align it such that the “irregular” tank faces the corner where the support ring of the SMMS has no dedicated holding bracket, then snap in from the top, carefully bending the holding brackets until the ring sits firm in its place. Can alternatively already be put into place before merging the SMMS with the DSA.

and for Subassembly 2:

1. TTA - Thermal Tent Assembly - Its top is towards the “eyes”, the “mouth” is close to the bottom.
2. PM-FPA - Payload Module - Focal Plane Assembly - Just like in real life, this is the most complicated assembly due to its geometry and fine parts. Apologies how this is a really delicate part. The stl file includes some supports as part of the model itself, refer to my gcode to know which additional supports I added in the slicer. As comparison to know which parts are supposed to be the actual model I added the stl of the part without supports as well. Also, when clearing this for assembly the secondary mirrors (the ones below the torus) came off together with the supports but I decided to share it already anyways.
   While technically it could be regarded as optional for this model, what would be a telescope without its actual mirrors? Once you managed to get the supports off with the mirrors still attached (at least the primary ones maybe), feed it into the TTA from the bottom. The parts should allow for enough flexibility such that with careful twisting and moving at angles back and forth (or rotating even) you should manage to manoeuvre the FPA into the TTA until the front facing focal plane sticks through the “mouth” opening of the TTA and the holding arms for the top mirrors sit firm against the corresponding protrusions below the top ring of the TTA. It is aligned correctly if by looking through each of the “eyes” you can spot a primary mirror in line behind it - and that's exactly the path that all the light of the universe took as it was collected by Gaia.
3. TT Top Cover - While technically part of this subassembly, I'd recommend first mounting the two subassemblies together (see just below) before adding the cover as final step to allow for at least some visual guidance. Once that is done, align the cover with the top opening of the TTA such that the two grooves of the TT Top Cover align with the corresponding protrusions of that top ring, then snap into place by firmly pressing into opening.

Merging the subassemblies:

1. Take the TTA and place it over the SMMS top ring until it rests on the DSA. Make sure that the “mouth” aligns with the cut off side of the top ring of the SMMS. On the inside make sure that the stuts of the PM-FPA sit somewhere close to the designated holding positions of the SMMS top. You can also slightly bend them away as the PM will be held in place quite well by the part of it that sticks through the TTA "mouth".
2. Gently push the TTA further down such that its outer wall sits between the pins from the DSA and the SMMS part. Be aware not to push on the part of the top ring directly above the “eyes” as it'll make your telescope look rather angry about it.
3. Once the telescope is put together, you may mount it with its backside onto the designated pin of the Display Stand. This pin has a smaller diameter than the counterpart opening of the SMMS but due to its angle towards the printing z-axis the pin should comes out thicker and is likely to require some careful shaving/filing as post-processing.

I highly recommend a set of fine tweezers and pliers for assistance and manoeuvring the parts into one another. Please also see the attached section views for guidance.

Comparison of the exploded view of the original spacecraft (left) and the CAD assembly for this model (right):

Note: the “tent” for the 3d model is “higher” as it also serves as the outside shielding of the SMMS and for assembly ease. Also, the top cover in the original seems to be part of the “tent” but is a separate model to allow for an easy colour change.

My model seen in the images was printed with the following filament(s):

• Prusament PETG Signal White for the TT Top Cover and the ASP
• Prusament PETG Jet Black for the SMMS (mine came of the printbed quite stringy, might be better to do in PLA)
• Prusament PETG Galaxy Black for the TTA, the SPA and the Display Stand
• extrudr XPETG Matt Blue for the FSA
• Prusament PLA Silver for the DSA, the PPTA and the PM-FPA - for the DSA I would actually rather recommend using PETG but this is the only “shiny” filament I've got so far

Particularly the more delicate parts I initially wanted to print in PETG (as that allows for a bit more bending than PLA) but for me PLA worked better as there was way less stringing and the supports were a bit easier for me to clear but your experience might be different, especially if you got lots more printing experience than me.

In general, please keep in mind that this is a delicate display model so, taking it apart a lot won't do the interfaces any good and parts will deteriorate. Feel free to glue things into place if you prefer permanent connections. My printout and assembled model holds in place quite well and I can easily lift it up on the tent and move it around freely without any of the other parts falling off or any parts on the inside becoming loose. 

However, this shouldn't excuse some problems still present in some of the current model files that I might get around to solving in a follow-up iteration. The shortcomings I've noticed in my printing and building experience were:

• The top cover doesn't sit as firmly as I would like it to.
• Similarly, the FSA didn't click into its holding position as well as I would like it to.
• The pins of the SMMS and the DSA don't engage as well to allow for a fixed connection of these two parts without adding the SPA.
• I realize that especially the PPTA is particularly flimsy and my ring broke as well when integrating but it wasn't a big issue as it somehow still sits firmly on its designated support.
• Obviously, the most difficult part to print and put into place is the PM-FPA. For now I had to accept that the secondary mirrors came off but their connections and support pillars will need some rework. Also, the interface with the SMMS to actually hold the struts of the torus in place doesn't really work on this minuscule scale. Not to mention that this part actually lacks a lot of even more delicate parts if you compare it to the engineering documentation of the actual telescope.
• The pin of the display stand comes out thicker than designed due to its orientation w.r.t. the printing z-axis. Thus, the pin requires some careful post processing to properly fit into the designated opening at the SMMS (bottom side, middle). 

Happy printing and assembling!

Information and (rendered) image sources:

1. “Sky-scanning complete”, taken from https://www.esa.int/ESA_Multimedia/Images/2025/01/Sky-scanning_complete_for_Gaia, Credit: ESA/Gaia/DPAC, Milky Way impression by Stefan Payne-Wardenaar
2. https://sci.esa.int/web/gaia/-/40128-overview
3. Original exploded view, see https://sci.esa.int/s/wK5xld8, Credit: ESA/ATG medialab
4. https://www.airbus.com/en/newsroom/press-releases/2016-09-airbus-defence-and-spaces-gaia-spacecraft-delivers-data-on-11
5. https://www.airbus.com/sites/g/files/jlcbta136/files/b23faf356fb340ff41f53796148ff169_infographics-gaia_en.pdf