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This sentence in the abstract:
' ... by performing a measurement of the gravitational redshift of the Sun and the Moon ... '
should be:
' ... by performing a test of the gravitational redshift of the Sun and the Moon ... '.
Moreover, the meaning of the following statement in the introduction was not very clear and led to unfortunate interpretation of the performance of the redshift test.
'The microwave link will allow for a measurement of the gravitational redshift due to the Sunʼs and the Moonʼs gravitational potential by ground clock comparison, expected to reach an uncertainty of 
and 
, respectively. The former is presently measured to the few per cent level [19, 20]; the latter is not experimentally determined yet. In case the optional atomic cesium clock is included in the STE-QUEST payload, the redshift due to the Earthʼs gravitational field will also be measured with an uncertainty of 
resulting in a factor 350 improvement over the current best measurements by Gravity Probe A [21].'
It is more carefully stated if replaced by:
'Through null-redshift tests for the gravitational field of the Sun and the Moon based on ground clock comparison, the microwave link will allow us to put bounds on possible violations of LPI at the expected levels of 
and 
, respectively [http://arxiv.org/abs/1404.4307]. The gravitational redshift for the Sun has been measured at the percent level [19, 20], whereas for the Moon it has not been experimentally determined yet.'