Interview, Fireside Chat, Podcast
a16z Podcast | New Year, New Horizons -- Pluto!
- The mission plans to utilize radio occultation to extract temperature and pressure profiles of Pluto's atmosphere and Charon's surface properties via signal refraction, requiring the transmission of a novel signal acquisition architecture to a modified spacecraft receiver.
- Scientists anticipate an exquisite profile of Pluto's temperature and pressure, radiometry measurements, and detection of bistatic radar signals, but predict that Pluto's atmosphere will likely collapse as the planet moves to apogee, necessitating arrival before this transition.
- Mission design accounts for plutonium power source degradation, with output expected to reduce from 300 watts to approximately 245 watts by arrival, alongside a requirement for a fresh supply of plutonium to limit first-year power loss to a few percent.
- Critical risks include the indefinite shutdown of the Department of Energy's plutonium processing facility due to a radioactive leak and the potential three-to-four-year timeline for obtaining necessary licenses, which conflicts with the mission's requirement for approval within six months.
- The team expects to acquire alternative plutonium from Russian storage facilities through State Department brokering and anticipates the spacecraft power budget reduction will force the implementation of the signal processing design into a single radiation-hardened FPGA.
- Development constraints involve the limited availability of early 2000s radiation-hardened FPGAs with approximately one million gates per device, requiring the entire system to fit within a single unit that will utilize 99% of available capacity.
- To accommodate these constraints, the team expects to implement legacy radar techniques by adapting them for a 10,000-element Finite Impulse Response filter, avoiding clever algorithmic recasting to ensure algorithmic stability within the device.
- Technical challenges include fundamental failures in language assembly processes when dropping custom algorithms onto programmable FPGA devices, potentially requiring a year of troubleshooting, and a design result with only five non-use gates remaining that may fail standard margin requirements.
- Operational protocols require a waiver of NASA's standard 15% to 25% margin requirements, as the FPGA design is expected to consume less than 1% of available gate capacity despite the tight constraints.
- The spacecraft computer may enter a "safe" mode due to a race condition involving JPEG compression time, the watchdog timer, and flash memory update commands, requiring the operations team to react within a 30-hour window to autonomously restart the timeline.
- The mission design anticipates a nine-year annual checkout cycle including rehearsals of occultation and radiometric measurement sequences before arrival.
- During the occultation phase, Deep Space Network stations at Goldstone and Canberra are expected to transmit four to five simultaneous signals, while the Ultra-Stable Oscillator will maintain frequency stability to one part in 10^13 to enable precision measurements over billions of miles.
- Received signals at Pluto are expected to be overwhelmed by noise, with an amplitude one-thousandth of the waveform yet maintaining a signal-to-noise power ratio of one million to one, requiring prototype receivers capable of capturing narrowband signals for inversion processes.
- The Stanford Dish is planned to be repurposed from its original over-the-horizon function by replacing hydraulic motors with electric stepper motors derived from disk drive technology to enable high-precision, high-speed tracking.
- This hardware upgrade is expected to mitigate safety risks associated with high-pressure oil lines and the retirement of technicians familiar with original hydraulic systems while allowing the dish to detect leakage signals as faint as a millionth of a watt.
- The repurposed dish also anticipates capability to search for alien signals if equipped with high-performance receivers capable of isolating and excising radio frequency interference from the Bay Area environment.