SHIPS: Source Highlighter for IPS

SHIPS is a Python tool for scheduling astronomical observations of celestial sources for Interplanetary Scintillation (IPS) studies. It reads source catalogs and computes rise/set times at the Ooty Radio Telescope (ORT), Tamil Nadu, India, with special emphasis on sources within 90° of the Sun—the optimal condition for IPS observations.

Features

• Flexible Catalog Input: Supports both FITS and TXT format source catalogs with flexible column naming
• IPS-Optimized Filtering: Automatically identifies sources within 90° solar elongation, ideal for scintillation studies
• IST Time Conversion: Computes rise/set times in Indian Standard Time (IST) for ORT operations
• Date-Based Scheduling: Generates schedules organized by observation date for convenient planning

Installation

Clone the repository and install dependencies:

git clone https://github.com/HardikMedhi/ships.git
cd ships
pip install -r requirements.txt

Usage

python source_highlight.py <catalog_file> <start_date> <end_date> [--schedule]

Arguments

• catalog_file: Path to source catalog (FITS or TXT format). Supported file extensions: .fits, .txt
• start_date: Start date in YYYYMMDD format
• end_date: End date in YYYYMMDD format
• --schedule (optional): Generate an optimized observation schedule by selecting the highest-flux source in each 5° elongation bin. Requires a flux column in the catalog

Examples

Generate complete observation schedule:

python source_highlight.py ort_cat.fits 20260320 20260430

This generates: all_sources_ort_cat_20260320_20260430.csv

Generate optimized schedule (highest flux per elongation bin):

python source_highlight.py ort_cat.fits 20260320 20260430 --schedule

This generates:

• all_sources_ort_cat_20260320_20260430.csv (all visible sources)
• schedule_ort_cat_20260320_20260430.csv (optimized schedule)

Output

The tool generates CSV files organized by observation date with columns: date, source_name, RA (J2000 HMS), Dec (J2000 DMS), rise (IST), set (IST), flux (Jy)

Each row represents one source observation with:

• date: Observation date (YYYY-MM-DD)
• source_name: Identifier from the input catalog
• RA (J2000 HMS): Right Ascension in Hours, Minutes, Seconds
• Dec (J2000 DMS): Declination in Degrees, Arcminutes, Arcseconds
• rise (IST): Source rise time in IST
• set (IST): Source set time in IST
• flux (Jy): Flux in Jansky (NaN if not available in catalog)

Data is organized by date (chronologically), then by elongation within each date (west to east).

Flux Information

If a flux column is detected (looking for: flux, flux_jy, flux_density, or s_peak), it is loaded in memory with units assumed to be Jansky. This enables generation of optimized observation schedules.

Optimized Schedule (--schedule flag)

When --schedule is used with flux data available, an additional file is generated that contains an optimized observation schedule. For each date:

• Sources are binned by elongation (5° bins)
• Only the highest-flux source is selected from each bin
• This minimizes observing conflicts while maximizing signal-to-noise

Observation Site

The tool is configured for the Ooty Radio Telescope (ORT) in southern India:

• Longitude: 76.66° E
• Latitude: 11.38° N
• Height: 2240 m

Input Catalog Requirements

Your source catalog must be in FITS (.fits) or TXT (.txt) format and include the following columns:

• source_name: Name/identifier of each source (required)
• RA Column (one of): ra, raj2000, or ra_j2000 (Right Ascension in J2000, HMS format, required)
• Dec Column (one of): dec, decj2000, or dec_j2000 (Declination in J2000, DMS format, required)
• Flux Column (one of, optional for scheduling): flux, flux_jy, flux_density, or s_peak (in Jansky units)

Note: The tool searches for RA and Dec columns case-insensitively with multiple naming options for flexibility. Flux information is automatically detected if present and is used for optimized scheduling with the --schedule flag.

Technical Details

• Uses Astropy for coordinate transformations and time calculations
• Coordinate Frames:
  • GCRS for solar elongation calculations (unaffected by Earth orientation)
  • CIRS for rise/set times (accounts for precession and nutation)
• Transforms all source coordinates to GCRS and CIRS frames at observation dates
• Converts between celestial (CIRS) and sidereal time systems
• Computes hour angles and rise/set times in IST (UTC+5:30)
• Implements solar elongation filtering for IPS-specific observation scheduling
• Optional flux-based scheduling: bins sources by 5° elongation intervals and selects highest flux per bin

Author

Hardik Medhi