Zodiacal Light Beyond Earth Orbit Observed with Pioneer 10

Understand

We reanalyze the Imaging Photopolarimeter data from Pioneer 10 to study the zodiacal light in the B and R bands beyond Earth orbit, applying an improved method to subtract integrated star light (ISL) and diffuse Galactic light (DGL).

• We found that there exists a significant instrumental offset, making it difficult to examine the absolute sky brightness.
• Instead, we analyzed the differential brightness, i.e., the difference in sky brightness from the average at high ecliptic latitude, and compared with that expected from the model zodiacal light.
• At a heliocentric distance of r<2 au, we found a fairly good correlation between the J-band model zodiacal light and the residual sky brightness after subtracting the ISL and DGL.