  Main belt asteroids (6070) Rheinland and (54827) 2001NQ8 belong to a small
population of couples of bodies which reside on very similar heliocentric
orbits. Vokrouhlicky & Nesvorny (2008, AJ 136, 280) promoted a term "asteroid
pairs", pointing out their common origin within the past tens to hundreds of
ky. Previous attempts to reconstruct the initial configuration of Rheinland and
2001NQ8 at the time of their separation have led to the prediction that
Rheinland's rotation should be retrograde. Here we report extensive photometric
observations of this asteroid and use the lightcurve inversion technique to
directly determine its rotation state and shape. We confirm the retrograde
sense of rotation of Rheinland, with obliquity value constrained to be >= 140
deg. The ecliptic longitude of the pole position is not well constrained as
yet. The asymmetric behavior of Rheinland's lightcurve reflects a sharp,
near-planar edge in our convex shape representation of this asteroid. Our
calibrated observations in the red filter also allow us to determine $H_R =
13.68\pm 0.05$ and $G = 0.31\pm 0.05$ values of the H-G system. With the
characteristic color index $V-R = 0.49\pm 0.05$ for the S-type asteroids, we
thus obtain $H = 14.17\pm 0.07$ for the absolute magnitude of (6070) Rheinland.
This a significantly larger value than previously obtained from analysis of the
astrometric survey observations. We next use the obliquity constraint for
Rheinland to eliminate some degree of uncertainty in the past propagation of
its orbit. This is because the sign of the past secular change of its semimajor
axis due to the Yarkovsky effect is now constrained. Determination of the
rotation state of the secondary component, asteroid (54827) 2001NQ8, is the key
element in further constraining the age of the pair and its formation process.
