Kinect launch in pr2_tabletop_segmentation without tabletop_detector

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Hi,

How is Kinect triggered to publish the point cloud in tabletop_segmentation service? I have created a local launch file that calls only the tabletop_segmentation service instead of all the other arm_nav, manipulations services. Its working fine, but I get an error saying that "no pointcloud2 is found". But when I trigger the rostopic echo /head_mount_kinect/depth_registered/points I see the points and then if I trigger the service it works fine. Is there something to trigger Kinect automatically than call the echo service all the time?

I am using ROS Groovy.

Any hints will be much appreciated!

Thanks in advance

Karthik