# What are the most common practical design specifications for antenna in space?

I'm writing my thesis on antennas for small satellite applications (cubesats). Apart from the electrical specifications related to the particular application there are also several other "practical" requirements related to the "harsh environment" that is space.

For instance, floating metal are dangerous for the antenna since they could collect charge and trigger a spark that could damage the device. Similar things could happen if we use material without a proper thermal dilatation factor or out-gassing. Also active electronics should be properly shielded from radiation.

My question is:

• Are there other practical design specification like the ones mentioned above?
• Maybe the Cal Poly university derived CubeSat standard website and the 1-3U specification may be a place to start ? – astrosnapper Sep 1 '20 at 16:40
• @astrosnapper thanks! i will have a look at it and come back here if i find something. – Paolo Squadrito Sep 2 '20 at 11:09
• Hi @PaoloSquadrito I've rolled back your post to the previous edit. While I understand that you'd like to concentrate on PCB antennas, we should not change the question after people have taken the time to write answers! Especially in this case to make the question better match your own answer that you posted after others have answered! That's just not how Stack Exchange works. – uhoh Sep 9 '20 at 23:50

Off the top of my head, here are a number of things you would need to address "apart from the electrical specifications". In reality, this is a great case for strong systems engineering in your satellite. Since there will be major tradeoffs between power, pointing, mass, and RF performance/throughput.

• Materials. This is mostly easy, since by definition the antenna will be metal, and in general metal is OK in space. However, if the metal has any sort of coating, you need to make sure that coating is compatible with the vacuum and atomic oxygen environment. Of course, the cables leading up to the antenna will have some sort of insulation, so you will need to worry about that as well.
• Coatings. Speaking of coatings, some satellites have specifically painted the antennas black/white to impart a radiometer-type spin on the satellite.
• Connectors. Yes, this borders on the electrical, but worth mentioning. A big hefty N-Connector is not going to fit into a small CubeSat very effectively
• Shape/type. You presumably already know the performance trade offs. But different shape/types will be packaged very differently on the satellite. A small patch, a simple dipole, and a dish all have different configurations. Reflectors also have the issue of needing some sort of remote feed. How do you intend to install that.
• Deployment. Other than a simple patch antenna mounted on the side of your satellite, all other antennas will need to deploy in some form after launch. How will you handle the deployment? The number of antennas will also impact your deployment, especially if you need to arrange them in a particular way to get the right beam pattern or polarization.
• Vibration. Presumably your satellite will ride to orbit on a noisy, vibrating, shaking rocket. Your antenna will have to be able to survive that vibration in a stowed configuration, and still be able to deploy and perform adequately.
• Thermal. The antenna will see extreme temperature swings throughout the orbit. You will need to make sure any thermal deformation is acceptable to the antenna's performance.
• Shadowing. The antenna is no good if it ends up shadowing the satellite's solar panels. Sure, maybe through the magic of membranes and composites you can deploy a 1 m dish off a 3U CubeSat, but if it shadows all the solar panels, then it is mission killing.
• Mass. Rarely do we worry about that in ground based applications, but in space, the mass of your antenna may make or break your mass budget. Sure you could get 20 dB out of a nice fancy antenna, but if it is triple the mass of your 4 dB antenna, then it may be game over.
• Beam width. Smaller beam width will increase your throughput. But you will now need to point the spacecraft, perhaps very accurately. This will impact the requirements on the attitude control subsystem, and in turn might have an impact on the power budget.
• Ground station compatibility - are you planning on having a dedicated ground station? Or are you hoping to utilize other networks like SATNOGS. There may be second-tier "electrical" considerations such as modulation type and polarization.
• somewhat related, though these mostly apply to larger satellites with dish antennas large enough to be heat leaks. : Why is Sentinel 3B's dish antenna overwrapped with metallized film? and When did deep-space probes start getting wrapped in germanium-coated film? – uhoh Sep 8 '20 at 23:12
• OP edited the subject to be more specifically related to PCB based antennas. My original answer was generic to all antenna types. Some of the emphasis will change for PCB antennas, but most of the points still hold true. – Carlos N Sep 9 '20 at 19:22
• I've rolled back the question to the previous version as mentioned here. – uhoh Sep 9 '20 at 23:52
• I'm not sure how the radiometer addresses the "harsh" environment of space, but I'd really like to see a reference for smallsats that "have... painted... antennas black/white to impart a radiometer-type spin..." I know about [these](satellite.space.stackexchange.com/q/27124/12102) but I think that those were separate paddles. So to this end I will ask a new question about antennas on smallsats that have had clever dual uses. upon further inspection I realized that Mariner's paddles are added to the ends of the solar panels, so they're not exactly separate either. – uhoh Sep 10 '20 at 0:06
• @uhoh - I don't have the time to go digging, but a number of the early AmSats used painted antennas, which in turn were often made out of hardware store measuring tape. – Carlos N Sep 10 '20 at 18:30

• The band you are transmitting on
• The type of antenna (your cubesat will likely significantly impact the choices you have here, but there are many types of antenna with many advantages and disadvantages)
• The output power (if it is an isotropic antenna, this is simpler, but if it is directional then you will need to consider the next thing)
• The antenna gain (due to design, and how it is impacted by imperfections/other things)
• Atmospheric absorption - the atmosphere is a strong absorber of some bands, and is completely transparent to others. The band affects the wavelength, which affects antenna size and effective aperture
• The size of the ground station, and its capacity to receive your signal (are you trying to pick this thing up with a whip antenna, or a giant radiotelescope?)

You use these and some other constraints to design your link budget, that determines how much power you need to transmit in order to receive X amount of power at the receiver (whether you have a single antenna for transmit/receive on the cubesat or not, but if not you'll have to do this twice, once for uplink and once for downlink. There are various reasons to do it that way, and various reasons not to).

Finally, design your antenna so that it won't interfere with other electronics and it won't get destroyed/have its signal degraded by the ambient radio background.

• Thanks @Camille Goudeseune for the edits, it definitely improved the answer – Michael Stachowsky Sep 1 '20 at 17:14
• This seems to mostly address what the question excludes: "Apart from the electrical specifications related to the particular application there are also several other 'practical' requirements related to the 'harsh environment' that is space." – uhoh Sep 2 '20 at 2:36
• Thank you for the time spent in giving an answer. Anfortunatelly as @uhoh said this answer mostly address what i excluded in the first place – Paolo Squadrito Sep 2 '20 at 11:08
• Oops, sorry about that! – Michael Stachowsky Sep 2 '20 at 14:37

Here is what I've found after specifically researching a bit about PCB antennas specifically:

• Temperature Variation:

Important to any discussion of small spacecraft structure is the material of the structure itself. Typically a spacecraft’s structure is made up of both metallic and non-metallic materials. Metals are commonly homogeneous and isotropic, meaning they have the same properties at every point and in every direction. Non-metals, such as composites, are normally neither homogeneous nor isotropic. Material choice is driven by the operational environment of the spacecraft and must ensure adequate margin for launch and operational loads, thermal balance and thermal stress management, and by the sensitivities of the instrumentation and payload to outgassing and thermal displacements. [1]

• Out-gassing:

In the spacecraft industry, outgassing refers to the sublimation or evaporation of materials as those materials are taken to a high-vacuum environment like space. The material that is lost to outgassing can find its way onto sensitive components and possibly affect a mission’s success. [2]

CubeSat materials shall satisfy the following low out-gassing criterion to prevent contamination of other spacecraft during integration, testing, and launch. A list of NASA approved low out-gassing materials can be found at: http://outgassing.nasa.gov. [3]

• CubeSats materials shall have a Total Mass Loss (TML) < 1.0 %
• CubeSat materials shall have a Collected Volatile Condensable Material (CVCM) < 0.1 %
• Atomic Oxygen:

Atomic Oxygen can be found in low earth orbit, between 100 and 1000 km. This atomic version of oxygen is created by the interaction of UV light and molecular oxygen. These atoms are very corrosive and, over time, will oxidate metals, specially silver and osmium, and will erode polymers. [4]

• Electrostatic Discharge:

The basic source of in-space charging problems is the charged particle environment (CPE). If that environment cannot be avoided, the next sources of ESD threats are items that can store and accumulate charge and/or energy.Ungrounded (isolated) metals are hazardous because they can accumulate charge and energy. Excellent dielectrics can accumulate charge and energy as well. Limiting the charge storing material or charging capacity is a useful method for reducing the internal charging threat. This can be accomplished by providing a bleed path so that all plasma-caused charges can equalize throughout the spacecraft or by having only small quantities of charge-storing materials. Antenna elements usually should be electrically grounded to the structure.Implementation of antenna grounding will require careful consideration in the initial design phase. All metal surfaces, booms, covers, and feeds should be grounded to the structure by wires and metallic screws (dc short design). All waveguide elements should be electrically bonded together with spot-welded connectors and grounded to the spacecraft structure. These elements must be grounded to the Faraday cage at their entry points. [5]

• +100 for a thorough and well-sourced answer! – uhoh Sep 9 '20 at 10:45