Citation
Abstract
This study examines link analyses involving a lander on the surface of Venus where high atmospheric temperature and pressure are not conducive to the use of modernday digital electronics. We explore the use of older analog technology such as AM/FM radio, which is more amenable to Venusian surface conditions. The lander will have a communications link to an orbiting spacecraft at an altitude of 240 km, which will receive the lander’s transmitted signal. The orbiter will perform the necessary conditioning and processing of the received signal and package it for relay back to Earth on an interplanetary link. The visibility time per a particular orbit is on the order of a few minutes. We consider three scenarios for returning the data to Earth: 1) On-board processing and detection of signal frequencies on the orbiter to be telemetered back to Earth; 2) Reception of the full 1-MHz analog band at the orbiter which in turn gets sampled, digitized, and encoded for transmission back to Earth; and 3) Reception of the full 1-MHz band directly back to Earth to be recorded on an open-loop receiver and processed in non-real time. For scenario 1: If one makes use of 100 sensors whose frequencies are detected using onboard processing at the orbiter receiver within the 1-MHz bandwidth, then one would have a data rate of 1400 bps, assuming 14 bit/sample resolution at 1-sec updates. Note this can be further refined as the design evolves. Thus, for N sensors, we would have a 14 ´ N bps data rate. For scenario 2: If one wishes to ship the entire 1-MHz band received at the orbiter back to Earth, this would involve down-conversion, digital sampling at the Nyquist rate (for 2 bit/sample), and encoding with a rate ½ error-correcting code resulting in an effective ~4 Msps rate back to Earth for later processing and detection of the sensor data. This is a very high data rate and the feasibility of achieving it needs to be assessed on the Venus-Earth relay link, as well as evaluating on-board storage of the recorded data between orbits. For scenario 3: A direct-to-Earth (DTE) link from the lander to a DSN 70-m station is feasible at L-band at a frequency of 1.67 GHz, as there exists available equipment. Reasonable power levels are achieved for this option for the case of six sensors (six AM sidetones), which will be discussed here.
Details
- Volume
- 42-236
- Published
- February 15, 2024
- Pages
- 1–18
- File Size
- 1.0 MB