Here is a very basic solution :

extends Node2D
var angle = 0
var rotation_speed = 1
var center
var radius
# Called when the node enters the scene tree for the first time.
func _ready():
center = $Sprite.position
radius = $Sprite2.position.distance_to(center)
func _process(delta):
angle = lerp(angle, deg2rad(360), rotation_speed * delta)
var coord = (Vector2(cos(angle), sin(angle)) * radius) + center
$Sprite2.position = coord
if angle > deg2rad(358):
angle = 0
You will have to find a way to have a linear speed and handle the looping