Fix camera's orientation

PX4 Autopilot
1

I am using the follwing SDF file to launch my drone. What I want to do is fix the camera to the drone in such a way that it always faces down irrespective of the drone’s orientation. It should have no changes in orientation whatsoever. How can I do it? The code is -

<?xml version="1.0" encoding="UTF-8"?>
<sdf version='1.9'>
  <model name='x500_mono_cam_down'>
    <self_collide>false</self_collide>
    <include merge='true'>
      <uri>x500</uri>
    </include>
    <include merge='true'>
      <uri>model://mono_cam</uri>
      <pose>0 0 .10 0 1.5707 0</pose>
      <name>mono_cam</name>
    </include>
    <joint name="CameraJoint" type="fixed">
      <parent>base_link</parent>
      <child>camera_link</child>
      <pose relative_to="base_link">0 0 0 0 1.5707 0</pose>
    </joint>
    <plugin
      filename="gz-sim-odometry-publisher-system"
      name="gz::sim::systems::OdometryPublisher">
      <dimensions>3</dimensions>
    </plugin>
    <plugin
      filename="gz-sim-joint-state-publisher-system"
      name="gz::sim::systems::JointStatePublisher">
    </plugin>

    <plugin
      filename="gz-sim-pose-publisher-system"
      name="gz::sim::systems::PosePublisher">
      <publish_link_pose>true</publish_link_pose>
      <use_pose_vector_msg>true</use_pose_vector_msg>
      <static_publisher>true</static_publisher>
      <static_update_frequency>1</static_update_frequency>
    </plugin>
  </model>
</sdf>