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GRBBeta

GRBBeta and its Mission

GRBBeta is a technology demonstration mission whose main mission is to validate the technology for the future constellation of CAMELOT nanosatellites, which will be used to record and accurately locate gamma-ray bursts from space.

GRBBeta was created with the financial support of the Ministry of Education, Research, Development and Youth of the Slovak Republic. The project is carried out by the Technical University of Košice, Faculty of Aeronautics, and partners from various foreign institutions are collaborating on the project.

GRBBeta is a 2U CubeSat satellite. The dimensions of the satellite in the folded state (without deployed antennas) are 10 cm x 10 cm x 22.7 cm. The maximum mass of the satellite according to the standard for 2U is 2,66 kg.

The satellite contains the essential subsystems required for energy acquisition and storage, satellite orientation maintenance, communications, data storage and other necessary subsystems. The mission will also test some new subsystems. An advanced positioning module and a module for instant messaging over the Iridium satellite communications network. A pair of science facilities is also on board.

In addition to the science experiments, a digital converter will be available for radio amateurs to send messages via our satellite.

It is scheduled for launch on July 9, 2024. It will be carried into orbit by an ARIANE 6 rocket from the European Space Agency.

The supplier of the satellite platform is the Slovak company SPACEMANIC Ltd.

EDDIE

Eddie is the main computer unit of the GRBBeta satellite. This on-board computer is based on the MSP430 microcontroller and FreeRTOS firmware.

MURGAS

Spacemanic Murgas TRX is a nanosatellite transmitter module for communication in UHF or VHF frequency bands.

EXPERIMENTAL TRANSMITTER

Experimental transmitter in S-band
It is a transmitter for the 2.4Ghz amateur radio band. This experimental transmitter allows data transmission up to 2mbps.

VAC

In order to achieve accurate orientation of the satellite, AOCS VAC system has been selected. This compact system contains electromagnetic actuators, a trio of reaction wheels and sensors - magnetometer and sun sensors for precise body manoeuvring.

Composition of the GRBBeta

Scientific experiments on GRBBeta

GRB detector

The main scientific experiment is a gamma-ray detector at the heart of which is a scintillator, a flat caesium iodide crystal measuring 75 × 75 × 5 mm that emits gamma photons of visible light when hit by a photon. These are subsequently detected by silicon photomultipliers. The detector, encased in a dark polyvinyl fluoride film (tedlar), is housed in a 1 mm aluminium sheet box and placed externally on one of the sides of the nanosatellite body.

The signal from the photomultipliers is fed to an analogue amplifier and shapers, then sampled by an A/D converter whose output is processed by an field programmable gate array (FPGA). The detected waveforms (light curves of candidate gamma bursts) are then processed and stored by a 32b microcontroller. The entire signal path mentioned above, including the input photomultipliers, is duplicated for redundancy (and also to increase the overall sensitivity in case both channels are functional).

Comparison of the light curves eventually recorded by the detector with the light curves of the same flashes recorded by other existing gamma-ray observatories will allow to verify the basic idea of CAMELOT, i.e. the feasibility of localizing the sources of the flashes based on precise GPS timing.

The detector development is led by Andras Pal at Konkoly Obseravatory in Budapest. The scientific analysis of data from GRB detector is led by prof. Norbert Werner from the Faculty of Science of Masaryk University in Brno.

LuvCAM

The secondary scientific payload is a miniature camera sensitive in the ultraviolet part of the light spectrum. It will be a technology demonstrator and the smallest astrophysical camera in space. The results of the measurements of the degradation of the imaging chip in space will be used for future upcoming missions focusing on observations in the UV region, such as the QUVIK mission. A team from the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics is in charge of preparing the experiment in cooperation with Brno Observatory and Planetarium.

Information for radio amateur enthusiasts

Basic information on GRBBeta satellite reception

NORAD ID: TBD
Callsign: HA2GRB
UHF Downlink frequency: 436.785 MHz +/- Doppler shift
VHF Downlink frequency: 145.935 MHz +/- Doppler shift
SBand Downlink frequency: 2405.000MHz +/- Doppler shift
Modulation: GMSK, CW
Encoding: G3RUH 9k6 baud (UHF, VHF)
Morse: 20 WPM
Protocols: AX.25, Morse
Transmitting power: 1W (30dBm)
Onboard antenna: Dipole
Antenna polarization: Linear

Orbital parameters/Preliminary TLE

1 60237U 24128C   24248.76563864  .00013883  00000-0  11908-2 0  9994
2 60237  61.9959 324.8176 0015691 329.6689  30.3490 14.97679081  8510

Message types

AX.25 TRX beacon packet
AX.25 message
CW data beacon
Ground Station communication

The transmission period is following

TRX UHF AX.25 beacon every 90s
TRX UHF AX.25 message every 270s
TRX UHF Morse beacon every 180s

There are offsets applied between transmissions.

Example of decoded AX.25 TRX beacon packets

Data in AX.25 TRX beacon packet values are comma-separated.

1:Fm HA2GRB To CQ [10:44:13R] [AA] [+++++++]
U,600,1291714,85,0,2723,2766,2650,0,,187,263,95,145

Explanation:

Beacon identification [U – UHF, V – VHF]
Uptime since reset [s]
Uptime total [s]
Radio boot count
RF segment reset count
Radio MCU act. temperature [0.01°C]

RF chip act. temperature [0.01°C]
RF power amplifier act. temperature [0.01°C]
Digipeater forwarded message count
Last digipeater user sender’s callsign [ASCII, 6 spaces means nobody yet]
RX data packets (AX25 with CRC matched, includes CSP and digipeater packets)
TX data packets (includes CSP and digipeater packets)
Actual RSSI, ((value / 2) – 134) [dBm]
Value of RSSI when carrier detected – after preamble ((value / 2) – 134) [dBm]

Example of CW data beacon

Every CW beacon stars with "de ha2grb = " and ends with "ar".

de ha2grb = u5433r126t29p30 ar

Explanation:

u – total uptime [min]
r – reset number
t – temp MCU [°C]
p – temp Radio PA [°C]

u5433 = Uptime 5433 minute
r126 = 126 resets of radio
t29 = 29 degree of Celsius on DL radio MCU
p30 = 30 degree of Celsius on DL radio PA

Recommended TNC modem setup:

PACLEN 255
TXDELAY 15
MYCALL [Your callsign]
UNPROTO CQ (or callsign)

Receiving S-band transmission

Frequency (center): 2405 MHz
Modulation: GMSK
Baudrate: default 100kbaud, up to 2000kbaud

Decoder for the S-band:

Link: DECODER

Realtime decoding using HackRF:

hackrf_transfer -f 2367400000 -s 8000000 -a 1 -r – 2>/dev/null | sox -r 8000k -c 2 -t s8 – -t f32 -c 2 -r 1000k – | iq2iq -f cf32 -s 1000000 -d -100000 | mrc100_decode -r 1000000 -b 100000 -C /dev/stdin 2>/dev/null

hackrf_transfer -f 2367000000 -s 8000000 -a 1 -r – 2>/dev/null | iq2iq -f cs8 -s 8000000 -d -500000 -t cf32 | mrc100_decode -r 8000000 -b 2000000 -C /dev/stdin 2>/dev/null