Budget and Timeline - Risk Assessment (page 2 of 2)

 


Communications: Low

The possible failure points in the communication sub-system are the misalignment or malfunction of antennas between the Orbiter and the Lander. In order to address this concern, the dipole antenna on the Orbiter which is initially used to help the Orbiter align with the Lander location. This dipole antenna goes into receiver mode after initial deployment operations. In case the main HGA fails, the power level can be doubled and the dipole can be used as the antenna to communicate with the Orbiter satellite. Although, this back-up link would require about 4000s compared to the HGA’s 130s. But since the 3dB beam width of the dipole is much larger, the duration of transmission would still be sufficient to communicate the data to the satellite.

Similarly, the satellite also has a dipole antenna for receiving command and tracking instructions from the Earth station. Although, owing to the high path loss, this antenna cannot be used to transmit data back to earth.


Lander Power: Very Low

Stirling heat engines are a well-researched technology often used in space missions, particularly coupled with GPHS units as a heat source. NASA has been in development of specialized Stirling engines for some time as well. Because Stirling engines operate based on heat, the extreme temperature of Venus is not expected to pose serious challenges in the design of our main power system. If, through further analysis, we determine that the proposed 7 GPHS units are unable to provide the necessary power requirements for our system, we can modify the design in a straightforward manner to include additional GPHS units for additional power output from the Stirling engine.

The Sodium Sulfur batteries proposed for this mission are operational at high temperatures and provide a total of over 2400 Watt-hours of power. Our power requirements for electronic components and RF transmission will allow the batteries to remain over 99% fully charged for the duration of the mission. In the event of electrical power loss from the Stirling engine, the battery backup can power the electronics and transmissions for several weeks before being depleted. If the lander experiences a complete loss of power from the primary Stirling engine, the batteries should be capable of powering the cooling system and electronics long enough (at least 8 hours) to send a final transmission of the failure back to the satellite before the lander goes completely offline.


Cooling: Low

The two-stage Stirling cooler design has not yet been implemented, but is based on existing technology. The primary technical challenges involve coupling Stirling heat engines to Stirling coolers with minimal power loss for two stages of cooling. Insufficient heat lifting of one or both stages of cooling may result in damage to heat-sensitive electronic components. The availability of high-temperature electronics that can operate for up to 1 year in 300 °C environments to serve as a backup severely limits the total risk to the mission in the event of cooler failure.


Seismometry:  Low

Inprox Technologies has demonstrated successful operation of their seismometer in a simulated Venus-like environment. The current sensor is capable of detecting activity in the range of 1-30 Hz. While not ideal, this sensitivity is sufficient for collecting useful data on the seismic activity of the planet. A primary challenge with the seismometer will be packaging it in such a way that it can be drilled directly into the surface of the planet. Manufacture of custom-designed auger bits is expected to be straightforward, thus lifting some of the requirements from the sensor packaging itself


Satellite: Very Low

Unlike the landing module, the satellite technology selected for this mission does not have unusually extreme mission requirements. The technology is readily available as satellites have become more common in recent years.