With a Probe Scan Strength of 72 points, you can scan down Level 4 Relic and Data sites.
For Limited and Standard Sleeper Cache sites (Level 4 data) you need a higher strength 85-100 points, and for the Superior Sleeper Cache (Level 5 data) you need a strength of 105 points.
PROBE STRENGTH BASICS:
1) To see your current probe strength, hover your cursor over the picture of your probes in the HUD.
2) As a "new" Alpha player be happy with starting probe strength 50-55 pts. This is enough for scanning Level 3 data/relic sites.
3) Pay to increase your Probe Scan Strength:
upgrade to "Sisters Core Scanner Probes" (5M = +4 pts of scan strength)
upgrade to "Sisters Core Probe Launcher" (25M = +10% scan strength)
buy "Poteque 'Prospector' Astrometric Rangefinding" implants AR-802 (1M = +2% scan strength)
buy "Poteque 'Prospector' Astrometric Rangefinding" implants AR-806 (23M = +6% scan strength)
fit "Scan Rangefinding Array I" (+5% scan strength) - can equip multiple with diminishing returns
fit "Scan Rangefinding Array II" (+10% scan strength) - only available to Omega players
Ship rigs "Small Gravity Capacitor Upgrade I" (+10% scan strength) - dependent on ship fitting
Ship rigs "Small Gravity Capacitor Upgrade II" (+15% scan strength) - dependent on ship fitting
4) Increase your SKILLS for better Probe Scan Strength:
Train "Astrometric Rangefinding" (+5% per Level) - Alpha players limited to Level 2
Train "Astrometrics" (+5% per Level) - Alpha players limited to Level 3
(for Heron) Train "Caldari Frigate" (+7.5% per Level) - Alpha players limited to Level 4
5) Buy an Astero (~100M) - best exploration ship for Alpha players
6) Buy a Buzzard (~25M) - good ship for Omega explorers, but I still prefer flying an Astero