Open-source investigative journalism has undergone an orbital revolution. Where human rights researchers once depended on hearsay or unverified local reports, commercial satellite constellations now provide unvarnished, timestamped optical and radar ground truth of any location on the planet.

However, many investigative newsrooms and independent researchers struggle to navigate the commercial remote-sensing ecosystem.

Confused by technical jargon—such as Ground Sample Distance (GSD), multispectral shortwave infrared, revisit frequency, and radar phase interferometry—investigators often waste limited grant budgets ordering expensive high-resolution imagery when free public satellites would yield superior evidentiary results, or vice versa.

This guide provides an exhaustive, comparative procurement and technical manual for investigative desks, evaluating the four primary tiers of orbital imagery: Free Public Optical (Sentinel-2 & Landsat), Daily Medium-Resolution Constellations (PlanetScope), Sub-Meter Very High Resolution (Maxar & Airbus), and All-Weather Synthetic Aperture Radar (Capella & Sentinel-1).

1. The Core Metrics: Ground Sample Distance vs. Revisit Cadence

In orbital remote sensing, there is an inescapable physical trade-off between spatial resolution (how small a feature you can see) and temporal revisit rate (how frequently the satellite photographs that exact coordinate):

                   THE REMOTE SENSING TRADEOFF TRIANGLE
                                     ▲
                                    / \
                                   /   \  SPATIAL RESOLUTION
                                  /     \ (Maxar WorldView: 30cm GSD)
                                 /       \
                                /         \
       TEMPORAL REVISIT        /           \  SPECTRAL BREADTH
       (PlanetScope: Daily)   /_____________\ (Sentinel-2: 13 Bands)

Ground Sample Distance (GSD)

GSD defines the physical distance on the Earth’s surface represented by a single pixel in an uncompressed image: * 30-centimeter GSD: Each pixel represents a $30\text{cm} \times 30\text{cm}$ square. Individual vehicle windshields, structural roof punctures, artillery craters, and crowd densities are sharply discernible. * 3-meter GSD: Each pixel represents a $3\text{m} \times 3\text{m}$ square. Entire buildings, ships at sea, bridge spans, and runway construction can be mapped, but individual vehicles blur into indistinct single-pixel blobs. * 10-meter GSD: Each pixel represents a $10\text{m} \times 10\text{m}$ square. City blocks, large agricultural burn scars, and regional flood zones are visible, but tactical military movements cannot be resolved.

2. Comprehensive Constellation Matrix

3. Tier 1: Free Public Monitoring (Sentinel-2 and Copernicus)

Before spending newsroom funds on commercial imagery, investigators should exhaust the European Space Agency’s Copernicus Open Access Hub / Copernicus Browser.

                           SENTINEL-2 SPECTRAL ADVANTAGE
                                         │
           ┌─────────────────────────────┴─────────────────────────────┐
           ▼                                                           ▼
     VISIBLE BANDS (B2, B3, B4)                                SHORTWAVE INFRARED (B11, B12)
  • Standard True-Color 10m RGB                             • 20m spatial resolution
  • Blocked by smoke, clouds, & dust                        • Penetrates dense wildfire & combat smoke plumes
  • Shows ground as human eye sees                          • Illuminates active hot spots & fresh soil turnover

When Sentinel-2 is the Winning Choice:

• Burn Scar and Fire Mapping: Combining Near-Infrared (Band 8) with Shortwave Infrared (Band 12) generates the Normalized Burn Ratio (NBR). When artillery barrages ignite agricultural belts, Sentinel-2 maps the destruction boundaries with zero procurement delay.
• Water Reservoir & Dam Depletion: Tracing drought weaponization or dam breaches using the Normalized Difference Water Index (NDWI).
• Maritime Anchorage Auditing: Detecting massive crude oil tankers (300m length = 30 contiguous pixels) idling off sanctioned ports.

4. Tier 2: The Time Machine (PlanetScope Daily 3-Meter)

The greatest obstacle in satellite investigations is cloud cover and temporal gaps. High-resolution satellites may take weeks before cloud-free conditions allow a tasking pass.

Planet Labs solves this by operating a constellation of over 200 shoebox-sized CubeSats (“Doves”) in sun-synchronous orbit, photographing the entire terrestrial landmass every 24 hours at 3-meter resolution.

INVESTIGATIVE TIME-SLIDER WORKFLOW:
  [OCTOBER 01] ──► Clear landscape; factory roof intact.
  [OCTOBER 02] ──► Low clouds; partial observation.
  [OCTOBER 03] ──► Ground truth strike: roof collapses, debris visible, black smoke plume.
  [OCTOBER 04] ──► Emergency service vehicles cluster around perimeter.

The Triage Technique:

1. Use PlanetScope to establish the temporal window of an event down to a single 24-hour cycle.
2. Once the exact date of destruction is proven via PlanetScope, order an archival, sub-meter Maxar image for that specific day to obtain forensic-grade clarity.

5. Tier 3: Sub-Meter Optical Precision (Maxar and Airbus)

When investigations require physical accountability—such as proving whether an unexploded bomb bears specific guidance fin geometries, verifying whether an impact was caused by an artillery shell or a precision cruise missile, or counting bodies in a courtyard—sub-meter resolution is legally mandatory.

WHAT 30-CENTIMETER GSD RESOLVES:
  ┌──────────────────────────────────────────────────────────────┐
  │ • Wheel vs. track marks in soft soil                         │
  │ • Individual human shadows extending from upright bodies     │
  │ • Damaged structural reinforced concrete rebars              │
  │ • Tail registration marks on commercial airliners            │
  │ • Anti-aircraft missile canister launcher tubes (erect/flat) │
  └──────────────────────────────────────────────────────────────┘

Procurement Rules for Journalists:

• Archive First, Tasking Second: Ordering a brand-new satellite pass (“tasking”) can cost $2,000–$5,000+ per collection area. However, querying the historical archive (imagery the satellite already captured on its own) is significantly cheaper ($15 to $25 per square kilometer with a minimum order size of 25 sq km).
• Non-Profit / Journalism Access: Both Planet Labs and Maxar offer subsidized non-profit grant programs (such as Planet’s Education and Research program and the Maxar News Bureau) that grant verified investigative desks free access to high-resolution imagery.

6. Tier 4: Penetrating the Invisible (Synthetic Aperture Radar)

When belligerents schedule military maneuvers under heavy fog, seasonal monsoon cloud decks, or nighttime darkness, optical satellites are completely blinded.

Synthetic Aperture Radar (SAR) bypasses atmospheric optics entirely: * The satellite emits active microwave radar pulses down to Earth and records the phase and amplitude of the backscattered signal. * Smooth Surfaces (Water, Flat Runways): Bounce radar waves away from the sensor $\to$ Rendered Pitch Black. * Vertical Metal Structures (Fences, Radar Dishes, Tanks): Act as dihedral corner reflectors, bouncing massive radar energy directly back to the satellite $\to$ Rendered Blindingly White. * Capella Space / Umbra 25cm SAR: Can resolve the metal silhouette of aircraft concealed beneath camouflage netting or parkings inside open-air hangar bays, 24 hours a day, through torrential rain.

By selecting the appropriate sensor for each investigative question, open-source researchers maximize their investigative budget and establish unshakeable orbital evidence.