Grizu-263A

Background

Grizu-263A was developed by the Grizu-263 Space Team of Zonguldak Bülent Ecevit University (ZBEÜ), a student team founded in 2016 whose earlier work centred on CanSat-class projects. The team and the satellite are named after the 263 miners who lost their lives in the firedamp explosion at the Kozlu coal mine in Zonguldak on 3 March 1992[1]. Work on a modular PocketQube platform began at the end of 2018; after about two years of development the flight model was delivered to the launch provider in October 2020[2]. Grizu-263A was the first PocketQube from Türkiye; the second, Hello Space’s 1P Istanbul, followed in 2023.

Objectives

The mission was a technology demonstration with an amateur-radio service. Its objectives were to[1]:

1. design, build and operate a spacecraft able to perform the basic functions of a satellite within a 1P envelope;
2. demonstrate a modular core bus to which payloads can be added without changing the core subsystems;
3. characterize the in-orbit behaviour of the passive magnetic attitude control and the efficiency of the power system through IMU, current and voltage telemetry;
4. give radio amateurs worldwide openly decodable telemetry, Doppler-observation opportunities and a digipeater that relays short messages uplinked from the ground.

The uplink was deliberately minimal: besides digipeater messages, the spacecraft accepted a command to change the telemetry period and the transmitter shut-down command required in the amateur-satellite service.

Outcome at a glance

Grizu-263A lifted off on 13 January 2022 on the SpaceX Transporter-3 rideshare and operated until its re-entry on 3 October 2023: 628 days, about 9500 revolutions, well beyond the expected year of active operation. Its primary communication objective was met, with telemetry received and shared by stations around the world; both downlink modes were still being received in several countries between 29 September and 1 October 2023, days before re-entry[1].

Architecture

Body-mounted panels on five faces feed the power system, which holds the battery and seven INA-type current and bus-voltage monitors: one on the EPS-to-computer line, one on the main bus and one on each panel. The on-board computer formats telemetry from these monitors, a three-axis IMU and a temperature sensor, and runs the digipeater. The radio transmits at 4800 Bd or 2400 Bd through a deployable quarter-wave monopole. If communication between radio and computer is lost, the radio reports an error code directly to the power system, so the fault can be handled without the computer[1].

flowchart TB
  SP["Solar panels on five faces"] --> EPS["EPS: battery, 7 current and voltage monitors"]
  EPS --> OBC["On-board computer: telemetry, digipeater"]
  EPS --> COMM["COMM: 2-FSK, 4800 and 2400 Bd"]
  EPS --> SENS["IMU, temperature sensor"]
  SENS --> OBC
  OBC <--> COMM
  COMM -. "error code if OBC link fails" .-> EPS
  COMM --> ANT["Deployable monopole"]
  ANT --> GS["ZBEÜ station and SatNOGS"]
  PMAC["PMAC: 4 AlNiCo-5 magnets, 12 HyMu-80 rods, unpowered"]

Power

The power budget filed for frequency coordination gives an average generation of 0.75 W and an average active consumption of 1.5 W, so the high-consumption mode was duty-cycled and the battery bridged eclipses and transmissions. The generation figure matches the sunlit mean predicted by Eq. 1 of the review without the eclipse factor, 0.71–0.86 W for five to six populated faces, which corresponds to an orbit average of 0.46–0.55 W[1].

Passive magnetic attitude control

Four 8 mm AlNiCo-5 cubes align one axis with the geomagnetic field and twelve HyMu-80 rods of 0.2 × 0.2 × 33.5 mm damp the motion; pre-flight dynamics were simulated with the Smart Nanosatellite Attitude Propagator. The review estimates the magnet moment from the AlNiCo demagnetization curve at 0.31 A·m² for isolated cubes and 0.91 A·m² for a stacked column, and derives the torque budget[1]:

The magnet oversizes the restoring torque by more than an order of magnitude; about 0.02 A·m² would have given a tenfold margin. With such a moment and magnet-to-rod distances of 20 mm or less, the stray field along the rods exceeds the geomagnetic field unless the rods lie within a fraction of a millimetre of the magnet mid-plane, and the IMU magnetometer measures a bias of several millitesla unless it sits far from the magnets. The PMAC entry explains both effects.

Radio link

The downlink used the coordinated EIRP of 20 dBm. Against a directional and an omnidirectional amateur station[1]:

• Directional, 4800 Bd
• Directional, 2400 Bd
• Omnidirectional, 4800 Bd
• Omnidirectional, 2400 Bd

Show the data as a table

Elevation (°)	Directional, 4800 Bd	Directional, 2400 Bd	Omnidirectional, 4800 Bd	Omnidirectional, 2400 Bd
5	−2.4	0.7	−14.9	−11.9
10	−0.7	2.4	−13.2	−10.2
15	0.9	4.0	−11.6	−8.6
20	2.3	5.4	−10.2	−7.2
30	4.7	7.7	−7.9	−4.8
45	7.1	10.2	−5.4	−2.4
60	8.7	11.7	−3.9	−0.8
75	9.6	12.6	−3.0	0.0
90	9.8	12.9	−2.7	0.3

At 4800 Bd, decoding needed a directional antenna above about 12° elevation and was never possible with the omnidirectional station; the 2400 Bd mode gained 3 dB, reaching directional stations down to 3° and omnidirectional ones only near zenith. The small margins agree with the early-mission observation that many network recordings lacked the signal-to-noise ratio needed for decoding.

Telemetry

Each frame carried 31 fields: identification and time (7), temperature (1), currents and voltages (14) and IMU data (9), with five frames every 10 s. All formats were published without encryption, and a Kaitai Struct decoder[3] in the SatNOGS database decoded the fields automatically[4].

Assembly, integration and test

Development followed a test-as-you-fly sequence of bench, engineering-model, thermal-vacuum and vibration tests. The flight model went through protoqualification vibration inside its flight pod on 21 September 2020 at the Vibration and Acoustics Laboratory of the Faculty of Mechanical Engineering of Istanbul Technical University: resonance surveys and random runs on all three axes, with no damage found. It was integrated into an AlbaPod in October 2020 and its kill switch released for flight[1].

Launch and early operations

The launch slipped from a window at the turn of 2020–2021 to 13 January 2022, when Transporter-3 lifted off from Cape Canaveral at 15:25 UTC with other PocketQubes including Delfi-PQ, HADES, EASAT-2, SATLLA-2A/2B, Unicorn-1 and Unicorn-2A/2D[5]. The ZBEÜ ground station received the first data on 14 January. Before catalogue numbers were assigned, the SatNOGS community tracked the satellite under the temporary identifier 99488; the first community decoders assumed a different line coding and failed until the framing was clarified, and frames were decoded on 19 January 2022. The satellite then received NORAD number 51025[1].

Orbital decay: forecast and outcome

The team expected about four years in orbit; Grizu-263A re-entered after 21 months. The review reconstructs the decay from a circular 525 km orbit with the Kennewell density model driven by the observed monthly $F_{10.7}$[6], a mean of 141 sfu over the mission, and constant $A_p=12$[1]:

With a priori ballistic parameters the model predicts 845, 774 and 666 days, 6–35% longer than observed, which is within the accuracy of a single-scale-height model and of the initial-orbit uncertainty: ±10 km of initial altitude moves the prediction between 669 and 885 days, while $A_p$ between 6 and 18 changes it by less than ±5%. With the effective parameter of $B_{\mathrm{eff}}\approx 0.050{\text{ m}}^2\text{/kg}$ and a constant 100 sfu the model gives 3.4 years, close to the pre-launch expectation. The difference between forecast and outcome is therefore largely solar: the flux was about 40% above the level that reproduces the four-year forecast, as Solar Cycle 25 rose faster than the 2019 forecast[7] and peaked earlier and stronger, as NOAA acknowledged in 2023[8].

Lessons learned

The complete case study, with figures and the reconstruction of the decay, is in the PocketQube review.