ZACUBE-1 (TSHEPISOSAT)

ZACUBE-1, also cataloged under the international designator 2013-066B and NORAD ID 39417, is a South African CubeSat operated by the Cape Peninsula University of Technology (CPUT). Launched in November 2013, it represents an early and meaningful step in South Africa's growing engagement with small satellite technology. The spacecraft carries a high-frequency beacon transmitter intended to support space weather research, positioning it as both a scientific instrument and a symbol of South Africa's ambitions in the new space economy. Its name, TshepisoSat, draws from the seSotho word *tshepiso*, meaning "promise" — an apt descriptor for a mission that signaled the beginning of a more active era in South African spaceflight.

Mission and Purpose

The primary scientific objective of ZACUBE-1 is to conduct space weather research through the operation of a high-frequency beacon transmitter. Space weather — encompassing the dynamic conditions driven by solar activity, including radiation, charged particle streams, and disturbances to Earth's magnetosphere and ionosphere — poses real risks to satellites, communications infrastructure, and power grids. Understanding these phenomena requires continuous, distributed measurement, and small satellites such as CubeSats offer a cost-effective means of contributing data to that global picture.

The high-frequency beacon aboard ZACUBE-1 can be used to probe the ionosphere by transmitting signals that interact with ionospheric plasma. Researchers analyzing the characteristics of those signals as received on the ground can extract information about ionospheric electron density, disturbances, and related phenomena. This kind of measurement is particularly valuable for a continent like Africa, where ground-based monitoring infrastructure has historically been sparse relative to Europe or North America, and where ionospheric dynamics can differ meaningfully from higher-latitude regions.

Beyond its scientific instrumentation, the mission also served an important educational and institutional function. By designing, building, and operating a satellite, CPUT gave its students and staff hands-on experience across the full lifecycle of a space mission — from engineering and integration through to launch operations and in-orbit data collection. This capacity-building dimension is a common and deliberate feature of university CubeSat programs, which treat the spacecraft itself as a learning environment as much as a research tool.

The word *tshepiso* — promise — embedded in the satellite's alternate name reflects this dual purpose: a promise of scientific contribution, and a promise of human capability development in a country where the space sector was still maturing.

Orbit and Tracking

ZACUBE-1 operates in a sun-synchronous orbit (SSO), a class of near-polar orbit in which the satellite's orbital plane precesses at a rate that keeps it aligned with the Sun throughout the year. This means the satellite passes over any given location on Earth at approximately the same local solar time on each successive pass, which is advantageous for consistent environmental measurements and for ensuring predictable illumination conditions — important for power generation via solar panels.

The spacecraft maintains an apogee of 595 km and a perigee of 540 km, placing it firmly in low Earth orbit. The relatively modest difference between these two values indicates a nearly circular orbit, which contributes to orbital stability and predictable ground track patterns. Its inclination is 97.8°, consistent with a sun-synchronous configuration and ensuring coverage of high-latitude regions including the polar zones.

ZACUBE-1 completes one orbit of Earth approximately every 95.9 minutes, meaning it circles the planet roughly 15 times per day. Over the course of multiple orbits, this rapid revisit cadence combined with the sun-synchronous inclination allows the satellite to sweep across a broad swath of Earth's surface, including the African continent, multiple times daily.

As of the time of writing, ZACUBE-1 remains in orbit. Given the altitude range at which it operates, the satellite experiences some degree of atmospheric drag, but the relatively high orbital altitude of around 540–595 km means atmospheric density is low enough to support a prolonged orbital lifetime. No reentry date has been recorded in current tracking catalogs.

The satellite can be tracked using its NORAD catalog ID 39417 and is identified in international space catalogs under the COSPAR designator 2013-066B. Both identifiers allow observers and researchers to access current two-line element sets (TLEs) and predict the satellite's ground track and visibility windows from specific locations.

Design and Operator

ZACUBE-1 was designed and built by the Cape Peninsula University of Technology, a public university based in Cape Town, South Africa. CPUT operates the French South African Institute of Technology (F'SATI), which served as the institutional home for the satellite development effort. The collaboration brought together academic researchers, engineering faculty, and students in a program that emphasized hands-on technical education as a core deliverable alongside the satellite mission itself.

The satellite follows the CubeSat standard, a widely adopted form factor in the small satellite industry that defines units (U) as cubes measuring 10 × 10 × 10 centimeters. CubeSats can be flown as single units or stacked in multi-unit configurations. ZACUBE-1 is a 1U CubeSat — a single cube — which constrains its mass, volume, and power budget significantly. These constraints make the design and integration of functional, reliable instrumentation a genuine engineering challenge, and successfully doing so is a meaningful technical achievement for any team, particularly one that may be undertaking its first satellite mission.

The manufacturer of the satellite is not recorded in public tracking catalogs, and the satellite's mass is similarly not publicly documented in available records. The operator of record is the Cape Peninsula University of Technology, which holds responsibility for the satellite's mission and operations.

ZACUBE-1 was launched on November 21, 2013, aboard a Dnepr rocket — a converted intercontinental ballistic missile repurposed for commercial satellite launches — from the Dombarovsky launch site near Yasny, in Russia's Orenburg Oblast. The Dnepr vehicle was a popular choice during this period for rideshare missions carrying multiple small satellites, offering a relatively affordable pathway to orbit for operators who could not afford a dedicated launch. The same launch carried a number of other satellites, reflecting the rideshare model that has since become even more prevalent in the CubeSat industry.

Significance and Current Status

ZACUBE-1 holds a notable place in the history of South African spaceflight. While South Africa has a longer history of engagement with space-related activities — including ground-based tracking infrastructure and remote sensing data acquisition — the development and launch of domestically built satellites remained rare for much of the country's history. ZACUBE-1, along with contemporaneous efforts by other South African institutions, marked a period in which the country began to build genuine in-house spacecraft engineering capability.

The satellite's focus on space weather and ionospheric research is especially relevant given South Africa's geographic and scientific context. The South African National Space Agency (SANSA) operates space weather services that provide data relevant to communications, navigation, and power grid management across the continent. Complementary satellite-based measurements of ionospheric conditions — of the kind ZACUBE-1 was designed to provide — contribute to a richer, more comprehensive picture of the near-Earth space environment over Africa.

For CPUT specifically, the mission validated the institution's capacity to carry a space project from concept through integration, launch, and operations. That institutional experience is difficult to replicate through coursework alone and represents a genuine asset for future missions. CPUT subsequently pursued further CubeSat development under the ZACUBE program, with ZACUBE-1 serving as the foundational mission in that lineage.

The satellite's current operational status is not confirmed in publicly available catalog data. Whether it continues to transmit or has fallen silent is not documented in the sources available to this publication. However, the spacecraft itself remains in orbit, as no reentry has been recorded.

The broader legacy of ZACUBE-1 is tied up in what it demonstrated: that a South African university team could conceive, construct, and deploy a functioning satellite, contribute to internationally relevant scientific objectives, and build a generation of engineers with real spacecraft experience. For a country still developing the depth of its space sector, that demonstration carried significance well beyond the technical specifications of a single 1U CubeSat. The name *TshepisoSat* — the promise satellite — proved, in that respect, to be well chosen.