The Raspberry Pi 4 (RPi4) is a powerful and inexpensive computer. We plan to use an array of eight RPi4s to control the six individual telescopes that make up the prototype element of the Condor Array Telescope and to handle scheduling and sequencing, preliminary data processing, data storage, and data archiving.
To test the configuration, we purchased four RPi4s each with 4 GB of memory back in March of this year. For each RPi4, we also purchased a heat sink with cooling fan and a 128 GB mSATA solid-state drive (SSD) together with an mSATA SSD "shield" that holds and supplies power to the SSD and attaches the SSD to the RPi4. The following figure shows one of the four RPi4s. Along the right side of the board, there is a gigabit ethernet connector (top), two USB 3 connectors (middle), and two USB 2 connectors (bottom). Along the bottom of the board, there is a USB-C power connector (left), two HDMI connectors (middle), and a stereo audio connector (right). And along the top of the board, there is a 40-pin general purpose IO header.
The following figures show the heat sink with cooling fan, the 128 GB mSATA SSD, and the mSATA SSD shield. The heat sink attaches to the top of the board, the 128 GB mSATA SSD is inserted into the mSATA SSD shield, and the shield mounts to the bottom of the board.
The following figure shows an assembled unit, with the RPi4 and heat sink with cooling fan on the top and the 128 GB mSATA SSD attached to the mSATA SSD shield on the bottom. The shield is equipped with a USB 3 connector, which connects to one of the two USB 3 connectors on the RPi4 and provides the RPi4 access to the SSD at the 5 gigabit per second bandwidth of USB 3.
A new version of the RPi4 with 8 GB of memory was just announced in late May. We recently ordered four of these new RPi4s, which should arrive in late June. These four will be configured identically to the existing RPi4s, which we will then use to form an array of eight RPi4s, four with 4 GB of memory and four with 8 GB of memory. We are currently developing and testing software for the RPi4 array.