Algorithm 1 A heuristic for min-max TDHTSP
1:	$W_1=W_2=0.5$;
2:	Determine a heterogeneous spanning forest using the proposed primal-dual heuristic.
3:	for $k=1,2$ do
4:	Let the connected targets reachable from the depot be a partition and label it as $P_k$.
5:	end for
6:	For $k=1,2$, derive $TourCos{t}_k$ and $Tou{r}_k$ for $r_k$ within $P_k$ (using an existing routing algorithm).
7:	$G\leftarrow max\left(TourCos{t}_k\right)$
8:	if $TourCos{t}_1\ge TourCos{t}_2$ then
9:	while $TourCos{t}_1\ge TourCos{t}_2$ do
10:	$W_1\leftarrow W_1+ϵ;W_2\leftarrow 1-W_1$
11:	Redetermine a target assignment using the proposed primal-dual heuristic and obtain the partitions $P_k^{\prime }$.
12:	for $k=1,2$ do
13:	Derive $TourCos{t}_k^{\prime }$ and $Tou{r}_k^{\prime }$ within $P_k^{\prime }$.
14:	end for
15:	if $Tou{r}^{\prime }$ is infeasible then
16:	break, {comment: $\because W_1\times cos{t}_{ij}^1>W_2\times cos{t}_{ij}^2$ for some $(i,j)$}
17:	else
18:	$G^{\prime }\leftarrow max\left(TourCos{t}_k^{\prime }\right)$
19:	if $G^{\prime }<G$ then
20:	$G\leftarrow G^{\prime }$
21:	for $k=1,2$ do
22:	$TourCos{t}_k\leftarrow TourCos{t}_k^{\prime };Tou{r}_k\leftarrow Tou{r}_k^{\prime }$
23:	end for
24:	end if
25:	end if
26:	end while
27:	else
28:	while $TourCos{t}_1\le TourCos{t}_2$ do
29:	$W_1\leftarrow W_1-ϵ;W_2\leftarrow 1-W_1$
30:	Redetermine a target assignment using the proposed primal-dual heuristic and obtain the partitions $P_k^{\prime }$.
31:	for $k=1,2$ do
32:	Derive $TourCos{t}_k^{\prime }$ and $Tou{r}_k^{\prime }$ within $P_k^{\prime }$.
33:	end for
34:	$G^{\prime }\leftarrow max\left(TourCos{t}_k^{\prime }\right)$
35:	if $G^{\prime }<G$ then
36:	$G\leftarrow G^{\prime }$
37:	for $k=1,2$ do
38:	$TourCos{t}_k\leftarrow TourCos{t}_k^{\prime };Tou{r}_k\leftarrow Tou{r}_k^{\prime }$
39:	end for
40:	end if
41:	end while
42:	end if
43:	return $Tou{r}_k,TourCos{t}_k$