Amateur Mission

What is the amateur mission?

In the ARICA-2 amateur mission, we will carry out a variety of operations so that amateur radio operators around the world can enjoy communicating with ARICA-2 (call sign: JS1YSD). During this mission, the following types of operation will be available:

Exchanging messages via ARICA-2
Downlinking image data taken by the satellite
CW beacon transmission

We plan to conduct one of these operating modes at a time for a specified period. Information such as the implementation schedule and duration will be announced as it becomes available (Links to the operation schedule and related announcements on the web and social media are currently under preparation).

Please see below for an explanation of each operating mode during the amateur mission.

１．Exchanging messages via ARICA-2

Message Upload and Download

ARICA-2 has 20 message slots, each capable of storing a message of up to 7 bytes for 48 hours. In addition to message upload and download functions, commands are also provided to downlink information indicating which station’s message is stored in which slot.

Message Echo

The uploaded message is downlinked as it is. This communication is possible even when all available message slots are already occupied.

２．Downlinking captured images

Using the infrared sensor, optical sensor, and machine learning capabilities onboard ARICA-2, the satellite will capture images of the Earth and downlink them via GMSK.

The image data is divided into packets of 100 bytes each. By specifying a packet ID in the uplink, the corresponding packet data can be downlinked.

The received data should be submitted through the ARICA-2 web page, where the image will be displayed as the data is updated. By combining the image data collected with everyone’s cooperation, we aim to reconstruct the images taken by the satellite.

３．CW beacon

During operation, ARICA-2 will transmit a CW beacon every 25 seconds, and we would appreciate your cooperation in receiving it.

For details of the data, please refer to the CW Beacon section on the lower left below, and for reception reports, please refer to the Reception Report section on the lower right below.

CW beacon

Reception Report

Communication Method

In the amateur mission, communication with ARICA-2 can be carried out using the settings shown below.

(*) The uplink uses a format unique to the satellite. Please send uplink data formatted as shown below via a TNC in KISS mode. For details, please refer to the “Uplink Format” section below.

Uplink Format

Uplinks to ARICA-2 should use the format: “0x42 (ASCII: B) + satellite-specific frame + AX.25 FCS.” The entire uplink must be fixed at 21 bytes.

The header and call sign are common elements used throughout the amateur mission. The green sections indicate data used in the “Exchanging messages via ARICA-2” operation mode, while the pink sections indicate data used in the “Downlinking captured images” operation mode.

Each operation mode is scheduled to be conducted during different periods and at different times; the two modes will not be operated simultaneously.

Within the 21-byte uplink command, any unused fields should be filled with arbitrary bits (for example, zeros) according to the bit length of that field.

Example:
During the “Exchanging messages via ARICA-2” operation mode, the Packet ID for downlink is not used, so the Packet ID for downlink should be set to “0000000000” in the uplink.

Header

The gray section in the figure represents the header of the uplink command and determines how ARICA-2 interprets the uplink data. During the amateur mission, please transmit the header exactly as shown in the gray section of the figure.

Mode

This field specifies the operation mode to be used. Use “0101” for the “Exchanging messages via ARICA-2” mode, and “0110” for the “Downlinking captured images” mode.

Call Sign

The call sign is limited to up to 6 characters (6 bytes). Therefore, please send the uplink without including an SSID.

Type Field

This field indicates the command type used in the “Exchanging messages via ARICA-2” operation mode.

type = “00”: Message download

This requests ARICA-2 to downlink the message stored in the specified message ID slot. If no message is stored in the specified ID slot, or if the ID value is invalid, a message indicating this will be downlinked.

type = “01”: Message upload
This requests ARICA-2 to store the transmitted message. If there is an available slot and no message from the same call sign is already stored, the message will be stored for 48 hours. Messages are automatically discarded after 48 hours. One slot may be used per call sign.

In addition, if a previously stored message from the same call sign still remains on ARICA-2 and a new message upload is requested from that call sign, the stored message will be overwritten with the new one without resetting the original storage period.

If the storage is successful, the satellite will downlink the ID of the slot in which the message was stored, along with the content of the stored message. If the message cannot be stored, a message indicating this will still be downlinked.

If 0x00 is inserted in the middle of a message, any data after that point will not be stored. For example, even if 0x41 0x41 0x41 0x00 0x42 0x42 is uploaded, only 0x41 0x41 0x41 will be stored.

type = “10”: Check stored message information
This requests ARICA-2 to check the messages it is holding and downlink information indicating whose message (call sign) is stored in which slot (ID). Information for empty slots is not downlinked. Depending on the size of the downlink data, the information is divided and transmitted across multiple packets.

Information for one slot is represented in 10 bytes, and since one packet consists of the address and PID (16 bytes) plus the message information, the total size ranges from 26 bytes (for 1 slot) to 86 bytes (for 7 slots).

If there are 1 to 7 stored messages (up to a maximum of 7 slots), the information for those 1 to 7 slots will be downlinked as a single packet.
If there are 8 to 14 stored messages (up to a maximum of 14 slots), the information for slots 8 to 14 will be added, and the data will be downlinked as a total of 2 packets.
If there are 15 to 20 stored messages (up to a maximum of 20 slots), the information for slots 15 to 20 will be further added, and the data will be downlinked as a total of 3 packets.
If no messages are stored, “ARICA-2 has no message...” will be downlinked.

type = “11”: Message echo
This requests ARICA-2 to downlink the transmitted message (upload message) exactly as it was sent. In this type, the satellite does not access the message storage slots, so communication with a message is possible even when all available slots are already occupied.

If 0x00 is inserted in the middle of a message, any data after that point cannot be received. For example, even if 0x41 0x41 0x41 0x00 0x42 0x42 is uploaded, only 0x41 0x41 0x41 will be received, and 0x41 0x41 0x41 will be returned.

Message ID for Downlink

In the “Exchanging messages via ARICA-2” operation mode, this field specifies the message to be downlinked when type = "00". When uplinking with any other type, please fill this bit field with an arbitrary value (for example, 0).

Upload Message

In the “Exchanging messages via ARICA-2” operation mode, this field specifies the message to be stored on ARICA-2 when type = "01", and the message to be echoed back when type = "11". The message length is fixed at 7 bytes. Any unused bytes or bits should be filled with zeros so that the total length is aligned to 7 bytes before uplinking.

Packet ID for Downlink

This command is used in the “Downlinking captured images” operation mode. You can specify, in binary, the packet ID you wish to downlink. Values from "0000000" correspond to packet IDs 1 to 25, and "0001100" corresponds to packet IDs 301 to 325.

Uplink Command Examples

The following shows an example command for actual uplink operation. The hexadecimal data shown below should be uplinked via a TNC in KISS mode. The value in parentheses is the FCS (frame check sequence).

During the “Exchanging messages via ARICA-2” operation mode, if the Aoyama Gakuin ground station (call sign: JS1YSE) uplinks a command to store the message “AAA” (ASCII: 41 41 41 00 00 00 00), the command is as follows:

42 F8 BD 40 00 4A 53 31 59 53 45 41 41 41 00 00 00 00 00 (9D 44)

During the “Exchanging messages via ARICA-2” operation mode, if the Aoyama Gakuin ground station (call sign: JS1YSE) uplinks a command to downlink the message stored in ID = 5, the command is as follows:

42 F8 BD 42 80 4A 53 31 59 53 45 00 00 00 00 00 00 00 00 (BE D5)

During the “Downlinking captured images” operation mode, if the Aoyama Gakuin ground station (call sign: JS1YSE) uplinks a command to downlink image data for Packet IDs 1 to 25, the command is as follows:

42 F8 BD 40 80 4A 53 31 59 53 45 00 00 00 00 00 00 00 00 (8F C1)

Uplink Data Generator

You can generate uplink data by entering the required information in the form below.

Clicking the Save button will save it as a text file.

Downlink Format

Exchanging messages via ARICA-2

The downlink format conforms to the AX.25 protocol.

The address field is left bit-shifted, and the entire data frame is downlinked after being processed by the UHF transceiver onboard the satellite with NRZI encoding, bit stuffing (zero insertion), 7E flag insertion (0x7E), and scrambling.

Example:

When the Aoyama Gakuin ground station (call sign: JS1YSE) uplinks a command to store the message “AAA,” the following data will be downlinked if the uplink is successful (as seen after demodulation in KISS format):

• If storage is successful (downlink message: saved 'AAA' at box: 1)
C0 00 94 A6 62 B2 A6 8A 60 94 A6 62 B2 A6 88 E1 03 F0 73 61 76 65 64 20 27 41 41 41 27 20 61 74 20 62 6F 78 3A 20 31 C0

• If storage fails (downlink message: message_box is full now)
C0 00 94 A6 62 B2 A6 8A 60 94 A6 62 B2 A6 88 E1 03 F0 6D 65 73 73 61 67 65 5F 62 6F 78 20 69 73 20 66 75 6C 6C 20 6E 6F 77 C0

Downlinking captured images

The specified packet data will be downlinked in the format “the following format + AX.25 FCS.” By submitting the binary data displayed in KISS mode, the image will be updated progressively. Details of the header and the submission destination are currently being prepared.

・Command ID

This field shows the ID number of the last command sent by the ARICA-2 team. During camera operation, the command IDs to be downlinked will be published as needed.

・Packet ID

This field indicates the packet ID number to be downlinked. The camera image data is divided into 97-byte segments and downlinked in packets numbered with Packet IDs from 1 to 325.

If you have any questions, please feel free to contact us.

E-mail : arica2-ama(at)phys.aoyama.ac.jp

(change (at) to @)

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