DIY ground stations for receiving satellite signals can be as cheap as $20-$30 or as expensive as $1500, and in this case more expensive is not necessarily better. Sprites are small, powered only by a solar panel, and many of them will be sending signals from orbit at once. Making sure that all of them can communicate with the ground successfully requires carefully selected software and equipment, along with some smart radio tricks.
Earlier, I highlighted the FUNcube dongle as a ground station option. Building the ground station was far in the future at the time, so I held off on purchasing one of the dongles. Now all FUNcube dongles have sold out. However, the team is using this opportunity to work on an updated and enhanced FUNcube Dongle Pro+. Conformance testing has already commenced, and shipping could occur as early as this month. The new dongle will cost between $200 and $250 with shipping.
However, the FUNcube dongle might not be the cheapest or even best option when building a ground station for the Sprites. Zac tested the original FUNcube dongle with middling results, and he is weighing additional options.
One of these options is the Carpcomm Ground Station 1. Carpcomm advertises their ground station as “the easiest way to set up a ground receiving station for cubestats.” It includes a box and antenna and is “fully compatible with the Carpcomm Space Communication Network.” The nice thing about Carpcomm is that the ground station is plug-and-play and does not require a computer; all signal processing is done on the cloud, and the box only needs a broadband internet connection to function.
The downside is two-fold. The ground station costs $1100 with a lead time of six weeks, and it depends on an external service for cloud data processing to decode packets. After one year of use, cloud data processing is no longer free.
Carpcomm is an interesting idea, and its use of cloud computing means that users can operate the ground station out of the box without needing to worry about decoding signals themselves. But $1100 is a steep price for a cloud box, and the Carpcomm website is unclear about what happens after the year of free cloud service expires. I contacted Carpcomm via Twitter in order to clarify this point but received no reply.
Currently, the most favored option in Ithaca is to use GNU Radio as the SDR and couple it with a receiving antenna. This option means more work for the Cornell team (which for me translates to a longer wait before beginning work on my own ground station) but has the advantage of being tailor-fit to the Sprite’s needs.