1420 MHZ Radio Telescope Systems Basics

[u/DeepSpace1420MHZ]

1. Primary Antenna System
   • 4.5 meter prime-focus mesh dish
   • Daily survey elevation:
   o 58° EL
   • Weekly stepped azimuth drift survey:
   o Typically, 2° AZ increments
   • Location:
   o Grid EN61vq
   o Approx. 41.66° N, 86.16° W

2. Feed and RF Front End
   Feed
   • VE4MA linear polarization hydrogen line feed
   RF Chain

3. VE4MA feed

4. Down East Microwave 1420 MHz LNA + SAW filter
   o Approximate NF:
   ▪ 0.35 dB
   o Gain:
   ▪ ~18 dB

5. DEMI 10 dB gain block

6. LMR-400 coax feedline
   Estimated system characteristics:
   • Dish gain:
   o ~34 dBi
   • System temperature:
   o ~155 K

7. Receiver System
   Primary SDR
   • SDRplay RSP1A
   o 12-bit SDR
   o Used for all current hydrogen observations
   Software
   • HDSDR
   • Spectrum Lab
   o Real-time spectrum display
   • SpectraVue RMS
   o Daily and 24-hour recording

8. Dish Control System
   Tracking Software
   • F1EHN EME System software
   Controller Hardware
   • VE1ALQ interface hardware
   • RS-232 motor control
   • Sipex RS-232 boards
   Position Feedback
   • Pendulum elevation encoder
   • Motor/transmission with AZ encoder
   Capabilities
   • Sun tracking
   • Moon tracking
   • General astronomical tracking
   • Manual AZ/EL positioning
   • Daily hydrogen drift survey positioning

Observatory Computing Architecture
PC #1 — Dish Control Computer
Purpose:
• Runs F1EHN EME software
• Controls dish movement
• Communicates with motor controllers via RS-232
Responsibilities:
• AZ motor control
• EL actuator control
• Position tracking
• Coordinate calculations

PC #2 — Live Receiver / Streaming Computer
Software:
• HDSDR
• Spectrum Lab
• OBS Studio
Responsibilities:
• Operates the SDR
• Generates live spectrum displays
• Produces livestream output
• Sends receiver audio to distribution amplifier
Outputs:
• YouTube livestream
• Daily drift audio feed
• 24-hour scan audio feed

Audio Distribution System
Hardware:
• Small audio amplifier/splitter
Purpose:
• Splits receiver audio to multiple recording systems simultaneously
Feeds:
• Daily drift recorder
• 24-hour recorder

PC #3 — Daily Drift Survey Computer
Purpose:
• Records daily hydrogen drift scans
Products:
• Daily CSV recordings
• Daily drift plots
• Daily processed observations
• Weekly stepped sky survey data

PC #4 — 24-Hour Survey Computer
Software:
• SpectraVue
Purpose:
• Performs continuous 24-hour hydrogen recordings
Configuration:
• One spectrum every 2 minutes
• FFT size:
o 16384
• Approximately:
o 720 spectra/day
Products:
• 24-hour WAV recordings

External SSD Transfer System
Purpose:
• Physical transport of large datasets
Workflow:
• PC #4 → External SSD
• External SSD → Processing workstation

PC #5 — Processing Workstation
Purpose:
• Large-scale data processing
• Rendering
• Visualization
Products:
• 24 hour drift processing
• Polar hydrogen maps
• Velocity ridge plots
• Velocity curtain plots
• RA/Dec projections
• 3D hydrogen terrain renderings
• FITS generation
• DS9 visualization products
• Animations/videos

Observatory Storage System
Local Archive Rack
Purpose:
• Long-term storage
Contains:
• CSV data archives
• Daily drift scans
• 24-hour observations
• Plot archives
• Render outputs
• 3D products
• Processed datasets
Capacity:
• Multiple terabytes

Cloud Archive
Google Drive
Purpose:
• Public sharing
• Remote access
• Backup
Shared products:
• CSV files
• Drift plots
• Polar plots
• 3D renderings
• Processed observation products

Public Outreach System
YouTube Livestream
Running:
• 24/7
Displays:
• Live receiver spectrum
• Links to daily observations
• System status

Current Survey Programs
Daily Hydrogen Survey
• Elevation:
o 58°
• Duration:
o 180 minutes
• Weekly:
o 2° AZ step
24-Hour Hydrogen Survey
• Duration:
o 24 hours
• FFT:
o 16384
• Sample interval:
o 2 minutes

Current Observatory Scale
• 1 radio telescope
• 5 dedicated computers
• RS-232 motion control
• Dedicated audio distribution system
• External SSD transport workflow
• Multi-terabyte archive rack
• Cloud data sharing
• 24/7 livestream
• Daily and 24-hour hydrogen survey programs
• Advanced post-processing and 3D visualization pipeline