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-**About the Complex**
 **Purpose**
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 The Terra integrated space environment simulator complex includes the following components:
+{{:en:терра.png?800|}}
   * Rotating globe – a simulator of the Earth’s surface reproducing the kinematics of translational motion of the satellite along the circumterrestrial orbit;
   * Flashlight – simulates the Sun and supplies the solar light flux needed for solar sensors to operate;
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-All parts of the construction set consist of commercially available and safe-to-use components.
+**Earth Simulator**
-**Principle of operation**
+Earth is represented by a globe that simulates:
+  * Geometrically scaled Earth surface observable from the satellite, measuring 130 cm in diameter;
+  * The kinematics of satellite motion over its assigned track along the equatorial orbit – either in real time or with supported time scaling (acceleration / deceleration), with particular surface areas photographed in the same conditions as the actual Earth surface is photographed by observation satellites (time, orbital variables, point coordinates, region coordinates);
+  * Conditions of communicating with the “Earth” (ground telemetry stations, GTSs) over telemetry and telecommand radio lines: LEDs of the respective “ground station” light up when it appears in the geometric visibility zone of the orbiter;
+  * Conditions of “Downlink” communication over a high-speed channel when the ground station enters into the geometric visibility zone of the orbiter.
-The functional "satellite" model, assembled from the construction set and programmed by user, is suspended by the thread. Then, it is slightly twisted and released, allowing the model to perform plane torsional oscillations. Depending on the task, the set of orientation sensors, the software, the composition and configuration of the main systems, and the payload, the "satellite" should stabilize its rotation on the gimbal (stop), then turn to one of the lateral surfaces on the "Earth" and take a photo of the "Earth's" surface in a given section. Variability of tasks is determined by different success criteria - maximum speed, different targeting algorithms, guidance accuracy, the simplicity and speed of implementation, minimum devices used in the arrangement, maximum information transmitted from the board, etc.
+{{:en:глобус.png?300|}}
-{{:ru::sx_constructor_3d.jpg |}}
+The satellite “orbits Earth” by being hung in the simulated “geomagnetic” field (within the current loop) and spins horizontally on its suspension thread – either freely or commanded by its user-programmed control system – as the globe simulating Earth rotates evenly in front of it, as if the orbiter were to fly along an equatorial orbit. The surface area of the globe of interest for photographing will sooner or later face the suspended orbiter. By this time the orbiter’s control system will have to orient and stabilize the satellite on its suspension rope while positioning the camera’s field of vision on area of interest with required precision. After the area is photographed, the data will have to be sent to users “on the ground” – this is accompanied by pointing a laser beam to the required “ground receiving station”.
+The globe is controlled from a PC via a USB port. The required functionality on the PC side must include controlling the rotation of the globe and managing a network of “ground telemetry stations” (GTSs, situated on the surface of the globe) along with “surface” centers receiving high-speed data traffic. These centers are located on the surface of the simulated “Earth” in known predetermined geographic points that are invariable in time.
+Conditions for communicating with “Earth” over telemetry and telecommand radio links are simulated computationally when a particular GTS on the surface of the globe occurs in the geometrical radio visibility zone of the string-suspended orbiter and by issuing the respective command to turn on/off the particular ground station. Once turned on, the ground station enters the telemetry reception mode by default.
+The conditions of data transfer from the orbiter toward “Earth” (to a photoreceiver on the surface of the globe) over a high-speed link are simulated by pointing a laser beam from the orbiter to a predefined market on the surface of the rotating globe. After normal orientation of the orbiter toward “Earth” is confirmed by a light beam falling on the light-sensing diode on the surface of the globe, data is transferred over a regular Wi-Fi link as long as the LED of the HF transmitter lights the required marker.
+Key properties of the globe:
+  * Diameter: 130 cm;
+  * Weight of the entire simulator (the globe with a driving motor with control system concealed inside): 40 kg;
+  * Globe weight: 20 kg, globe material: high-strength fiberglass plastic;
+  * High-contrast globe surface;
+  * A map with a view of Earth from the space and a meridian/parallel grid;
+  * Vertical globe rotation axis;
+  * Globe rotation speed can be varied continuously or in steps from the PC within the range of 0 to 1 RPM; rotation speed error is limited to ±2%; speed will be set at 0.2 RPM for the tournament;
+  * All drive components, electronics etc. are housed inside the globe;
+  * The globe connects to a 220 VAC outlet and the USB port of the control PC.
+Globe control system properties:
+  * Single-axis electric motor drive;
+  * Motor driver and driver control board;
+  * USB connection to the PC;
+  * Control system for “ground” telemetry stations and a light-sensing diode to detect the laser beam coming from the orbiter.
+All geometrical parameters of the globe and kinematic parameters of its rotation are aligned with capabilities of the simulated orbiter’s dynamic control system (response time, accuracy, number of degrees of freedom, continuous uptime) as well as capabilities of the orbiter payload (field of vision, exposure time, lighting conditions, data transmission rate) used in model settings for obtaining special information.
+**Sun Simulator**
+{{:en:прожектор.png?200|}}
+The Sun is simulated by a light source with light output properties approximating those of solar light. This light influences the positioning system of the model as well as the conditions for photographing globe areas by the camera integrated in the orbiter model.
+Key features of the simulator:
+  * Beam misalignment: 12° or less;
+  * Emission spectrum: closely approximating solar light;
+  * Diameter of beam concentrating 90% of power: 20 cm max;
+  * Irradiance in the visible-light range: approximating that of Sun at 1367 W/m² at a minimum distance of 0.2 m away from the light source;
+  * Safe for eyes (protection by sunglasses);
+  * The imitator is stationary throughout the experiment and can be easily moved by a single person to any distance between experiments;
+  * Power supplied from the regular 220VAC grid;
+  * A mounting system (a stand) enabling smooth adjustment of light source height (0.5 to 1.5 meters) and its inclination angle relative to the horizon (-60..60 degrees).
+The Sun Simulator must be turned on by the user before holding the experiment and turned off manually using a simple switch when the experiment is completed.
+**Earth Magnetic Field Simulator**
+The Earth’s magnetic field is simulated using a closed solenoid (Helmholtz coil) producing controlled magnetic flux directed through its vertical setting plane (the working plane). Such a loop acts as a simplified single-axis simulator of the Earth’s magnetic field.
+{{:en:рамка.png?200|}}
+The current loop is set on the floor and enables the Orbicraft construction set to be suspended on a thread so that the mass center of the construction set would end up in the working plane – the equatorial plane of the globe, about 80 cm above the floor, while letting the set rotate freely.
+Key properties of the solenoid:
+  * Uniformity zone (5%, 1°) matching the dimensions of the construction set;
+  * Material: aluminum frame, copper conductor;
+  * Dimensions: enabling free rotation of the string-suspended model inside with height adjustable within ±5 cm;
+  * Continuous operating time at full power: 4 hrs minimum;
+  * Power supply voltage: 27 V max;
+  * Safe for laboratory use.
+Principle of Operation
+A functional model of the “satellite” assembled using the kit and programmed by the user is suspended on a thread, then slightly twisted around and released, leaving it to spin back and forth in a single plane.
+Depending on the satellite mission, the choice of positioning sensors, the composition and integration of major systems and payload as well as software downloaded into it, the “satellite” will have to stabilize itself on the suspension string (to stop rotation), then turn one of its sides toward the “Earth” and take a picture of a particular area of the running Earth surface underneath.
+The variety of problems is determined by a multitude of criteria for success e.g. shortest response time, different guidance algorithms, guidance precision, implementation simplicity and speed, maximum amount of data delivered from the orbiter etc.
+The Setup
+Shown below is the overall appearance of the assembled Complex with the classic layout of Terra space environment simulator and the Orbicraft construction set as its component.
 **Stand scheme**
+{{:ru::sx_constructor_3d.jpg |}}
 {{:ru::схема_расположения.jpg?500|}}

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