Phobos 2

1. Historical Context and Detailed Objectives

The scientific gap that the Phobos 2 mission aimed to fill consisted of the exhaustive exploration of the Martian system and, as a priority, the satellite Phobos, combining orbital observations of the planet with a planned deployment of surface modules. Primary objectives focused on studying the interplanetary environment and solar emissions during transit, characterizing the plasma environment around Mars, investigating the Martian surface and atmosphere via infrared spectroscopy and magnetic mapping, and analyzing the morphology and composition of Phobos in detail.

Main Objectives:

• Study the solar wind and plasma interaction with the Martian ionosphere.
• Obtain thermal and mineralogical mapping of the Martian surface using infrared spectroscopy.
• Analyze the morphology, structure, and chemical composition of the satellite Phobos.

2. Vehicle Architecture and Main Subsystems

The spacecraft, based on the 1F model, had a dry mass of 2600 kg and reached 6220 kg including orbital insertion hardware. Electrical power generation was entrusted to sun-tracking solar arrays in a three-axis stabilized configuration. The propulsion subsystem for orbital insertion operated with a combination of nitric acid and amine fuel, complemented by 28 attitude control thrusters (twenty-four 50 N and four 10 N). For communications, the spacecraft featured a high-gain downlink with a rate of 4000 bits per second and an onboard data storage system of 30 megabits.

3. Payload and Scientific Instrumentation

The scientific payload consisted of a total of 25 instruments distributed for the multidisciplinary study of the Sun, the interplanetary medium, Mars, and Phobos, among which the following stood out:

• LIMA-D / DION: Laser and mass spectrometer to vaporize and analyze surface chemical composition.
• Termoskan: Thermal infrared scanning optical-mechanical radiometer and visible spectrum for thermal mapping.
• ISM: Infrared imaging spectrometer for mineralogical analysis.
• FREGAT: Television camera system for high-resolution mapping of Phobos.
• ASPERA: Electron spectrometer and ion mass analyzer for the plasma environment.
• APEX and LILAS: Gamma-ray spectrometers and cosmic burst detectors.
• PWS: Plasma wave and electric field meter.
• MAGMA / FGMM: Magnetometers for the study of magnetic fields.

4. Chronology and Mission Phases

The mission lifted off on July 12, 1988 from the Baikonur Cosmodrome aboard a Proton-K rocket. Following an interplanetary cruise phase in which solar and interplanetary medium observations were carried out, the spacecraft completed its insertion into areocentric orbit on January 30, 1989, immediately beginning the scientific phase. The program envisioned a gradual approach to the satellite Phobos and the subsequent deployment of a stationary module and a mobile hopper. However, on March 27, 1989, a critical failure occurred in the onboard computer or the backup radio system, causing the permanent loss of signal and cutting short the execution of the final phase.

5. Results and Discoveries

Despite its premature end, Phobos 2 managed to transmit 37 detailed images of Phobos covering nearly 80% of its surface with resolutions of up to 40 meters. Likewise, it provided highly valuable infrared spectroscopic data through the Termoskan and ISM instruments, and made key measurements on the solar wind, the Martian magnetic field, and plasma dynamics using the ASPERA and PWS equipment.

6. Legacy and Significance

Phobos 2 represented an ambitious technological and international effort in Soviet planetary exploration, laying methodological bases for the coordinated study of minor bodies and complex Martian orbits. Although the computer failure prevented the completion of the deployment of the landers on Phobos, the large amount of telemetry data, images, and plasma records obtained significantly enriched scientific knowledge about the interaction between Mars and the solar wind.