Connecting to Your TEMPEST CubeSat

The TEMPEST image ships pre-provisioned: instead of joining an external wifi network, each Pi Zero W broadcasts its own WiFi Access Point that workshop attendees connect to directly. For a fleet of 25 units, you'll see TEMPEST-1 through TEMPEST-25 advertised on the air — one SSID per satellite, matching its hostname.

Connecting from Your Laptop

  1. Open your laptop's wifi settings.
  2. Find the SSID matching the TEMPEST unit you want to use (e.g. TEMPEST-3).
  3. Join using the shared workshop key: Hack Space (default — your instructor may have rotated it).
  4. NetworkManager on the Pi runs DHCP + NAT in shared mode, so your laptop automatically picks up a lease in the 10.42.0.0/24 range.
  5. SSH into the satellite at its AP gateway address: bash ssh tempest@10.42.0.1 Default SSH credentials: tempest / tempest. Note that these are not the WiFi key — the AP password (Hack Space) gets you onto the network, the login above gets you a shell.

The Pi Zero W has a single radio, so each TEMPEST is its own isolated network — you can only be connected to one satellite at a time.

Rotating the AP Password

Once SSH'd in, change the PSK with:

sudo nmcli con modify tempest-ap wifi-sec.psk "new-password-here"
sudo nmcli con down tempest-ap && sudo nmcli con up tempest-ap

The down/up cycle is required — modifying the connection alone does not push the new key to the running AP. Every connected client (including your current SSH session) drops and must reconnect with the new key.

To check what the current PSK is set to (run as root for -s):

sudo nmcli -s con show tempest-ap | grep 802-11-wireless-security.psk:

Querying the AP Over Radio

If the satellite is in radio range but you can't see its SSID for any reason, the ground station can ask the FSW directly:

WIFI_INFO

The satellite responds with a WIFI telemetry packet containing the active SSID (32 bytes) and IPv4 address (15 bytes). See Command Protocol and the Telemetry Reference.

Imaging a Fresh microSD Card

If you're setting up a new TEMPEST from scratch (e.g. replacing a damaged SD card or upgrading the image), use Raspberry Pi Imager:

  1. Download and install Raspberry Pi Imager for your OS.
  2. Download the TEMPEST image that matches your OBC — pick the variant for the Pi Zero model in your unit:
    • TEMPEST v1 (Pi Zero W, deployed before 2025-01-01): TEMPESTv1-2.0.img.gz — SHA256: e54cd213f92620a667ebb81847de100791ffc617d98a7f76770968632c304b58
    • TEMPEST v2 (Pi Zero 2W, deployed after 2025-02-01): TempestV2-2.0.img.gz — SHA256: 67cca06f24f098bfa778dc5b13c7e40fffa8018e986cd3c7a62aab77afad22b5
  3. Take the microSD card out of TEMPEST by removing the four T8 screws on the X+ Solar Panel (the panel to your left when facing the RBF pin / charging port).

  4. In Raspberry Pi Imager, choose CHOOSE OS → Use custom and select the downloaded .img.gz file (Imager decompresses it on the fly), then choose your microSD card under CHOOSE STORAGE.

    Choose OS in Raspberry Pi Imager Use custom Select image file Choose storage Select microSD card Click Next

  5. Click NEXT. When Imager asks whether to apply OS customization, choose NO — the v2.0 images ship fully provisioned (hostname, AP, SSH, user, and FSW) and don't need any Imager-side settings. Confirm YES to overwrite the card.

  6. Wait for Raspberry Pi Imager to write and verify the image.
  7. Eject the microSD card, reinstall it in the Pi Zero, and power the satellite up. The Pi will shut down after ~30 seconds on first boot — this is expected. Insert and remove the RBF pin to reboot it.
  8. After a few minutes the AP will be live. Look for the tempest-ap SSID (matching the unit's hostname, e.g. TEMPEST-3) from your laptop and follow the Connecting from Your Laptop steps above.

Recovering an Unreachable Unit

If a satellite's AP is misconfigured or you've forgotten the PSK and can't SSH in:

  1. Power the Pi off, pull the microSD card, and mount it on your laptop.
  2. Edit /etc/NetworkManager/system-connections/tempest-ap.nmconnection — adjust the ssid or psk field directly.
  3. Reinsert the card and boot the Pi.

Alternatively, with physical access to the Pi (USB OTG keyboard + a USB→HDMI adapter), log in directly on the console and run the nmcli con modify commands from the Rotating the AP Password section above.