BlueBird 6 is Fainter than Block 1 Satellites

The mean apparent magnitude for BlueBird 6, the first Block 2 satellite of the BlueBird constellation, is 3.85 +/- 0.10 while that for Block 1 spacecraft is 3.30 +/- 0.07. So, BlueBird 6 is 0.55 magnitudes fainter. Likewise, the means of apparent magnitudes adjusted to a uniform distance of 1,000 km are 4.32 +/- 0.08 and 3.77 +/- 0.06, respectively. This difference is also 0.55 magnitude. The dimming is unexpected because the Block 2 satellites are ~3.5 times as large as Block 1. BlueBird 6 is only 17% as bright as Block 1 spacecraft per unit surface area. Possible explanations are discussed. All BlueBird satellites exceed the brightness limits recommended by the International Astronomical Union. However, they will be fewer in number than other satellite constellations.